Merge fix/storage-datensicherheit in main

Konfliktlösung: Speicher-Architektur des Branches (Formatversionierung,
Papierkorb, Backups, Instance-Lock, robuster Autosave) übernommen und die
dort fehlenden Korrekturen aus main darauf übertragen:

- Autosave gleicht das Manifest bei jeder Änderung mit dem Notizbuch ab
  (mark_dirty); per Taste N/Bild-ab angelegte Seiten gingen sonst nach
  einem Neustart verloren
- Start öffnet keine beschädigten Notizbücher automatisch und verwendet den
  Ordner eines nicht ladbaren Notizbuchs nicht wieder
- PDF-Export lädt nicht geöffnete Seiten nach (load_all_pages), verweigert
  unvollständige Exporte und meldet das echte Ergebnis an die UI
- Cargo.toml: minisign-verify und fs2

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/bin/crash_sim.rs

@@ -0,0 +1,221 @@
+//! Crash-Simulationstesthelfer für ink-notes.
+//! Wird von scripts/crash-test.sh verwendet, um unvollständige Schreibvorgänge
+//! und SIGKILL (kill -9) Robustheit zu verifizieren.
+
+use std::env;
+use std::path::Path;
+use std::process;
+use std::time::Duration;
+
+use glam::Vec2;
+use ink_notes::document::{Notebook, PageBackground, StylusSample};
+use ink_notes::spline::{finalize_stroke_with_config, SplineConfig};
+use ink_notes::storage::{
+    cleanup_orphaned_temp_files, load_notebook, load_page, save_manifest, save_notebook, save_page,
+    NotebookManifest, PageData,
+};
+
+fn run_init(dir: &Path) -> Result<(), Box<dyn std::error::Error>> {
+    let nb = Notebook::new();
+    let id = dir
+        .file_name()
+        .and_then(|n| n.to_str())
+        .unwrap_or("crash_test");
+    let mut m = NotebookManifest::new(id, "Crash Test Notebook");
+    m.sync_from_notebook(&nb);
+    save_notebook(dir, &nb, &mut m)?;
+    println!("[init] Initialized clean notebook in {:?}", dir);
+    Ok(())
+}
+
+fn run_worker(dir: &Path) {
+    let (mut notebook, mut manifest) = match load_notebook(dir) {
+        Ok((nb, m)) => (nb, m),
+        Err(_) => {
+            let nb = Notebook::new();
+            let id = dir
+                .file_name()
+                .and_then(|n| n.to_str())
+                .unwrap_or("crash_test");
+            let mut m = NotebookManifest::new(id, "Crash Test Notebook");
+            m.sync_from_notebook(&nb);
+            let _ = save_notebook(dir, &nb, &mut m);
+            (nb, m)
+        }
+    };
+
+    let spline_cfg = SplineConfig::default();
+    let mut stroke_counter = manifest.next_stroke_id;
+
+    println!("[worker] Started writing loop in {:?}", dir);
+
+    loop {
+        // Erzeuge neuen Strich mit einigen Samples
+        let base_x = (stroke_counter % 500) as f32;
+        let samples = vec![
+            StylusSample {
+                position: Vec2::new(base_x, 100.0),
+                pressure: 0.5,
+                timestamp: 0.0,
+            },
+            StylusSample {
+                position: Vec2::new(base_x + 10.0, 150.0),
+                pressure: 0.7,
+                timestamp: 0.01,
+            },
+            StylusSample {
+                position: Vec2::new(base_x + 20.0, 200.0),
+                pressure: 0.6,
+                timestamp: 0.02,
+            },
+        ];
+
+        let stroke = finalize_stroke_with_config(
+            stroke_counter,
+            &samples,
+            [0.0, 0.0, 0.0, 1.0],
+            &spline_cfg,
+        );
+        stroke_counter += 1;
+        manifest.next_stroke_id = stroke_counter;
+
+        let page = notebook.current_page_mut();
+        page.add_stroke(stroke);
+
+        let page_data = PageData::from(&*page);
+
+        // 1. Schreibe Seite atomar
+        if let Err(e) = save_page(dir, &page_data) {
+            eprintln!("[worker] Error saving page: {:?}", e);
+        }
+
+        // 2. Aktualisiere Manifest atomar
+        manifest.sync_from_notebook(&notebook);
+        if let Err(e) = save_manifest(dir, &manifest) {
+            eprintln!("[worker] Error saving manifest: {:?}", e);
+        }
+
+        // 3. Gelegentlich Gesamtsave (wie Autosave-Flush)
+        if stroke_counter % 5 == 0 {
+            if let Err(e) = save_notebook(dir, &notebook, &mut manifest) {
+                eprintln!("[worker] Error saving notebook: {:?}", e);
+            }
+        }
+
+        // 4. Evtl. neue Seite anlegen und sofort sichern, bevor Manifest aktualisiert wird
+        if stroke_counter % 25 == 0 {
+            let page_idx = notebook.add_page(PageBackground::DotGrid);
+            notebook.current_page_index = page_idx;
+            let new_page_data = PageData::from(notebook.current_page());
+            if let Err(e) = save_page(dir, &new_page_data) {
+                eprintln!("[worker] Error saving new page: {:?}", e);
+            }
+            manifest.sync_from_notebook(&notebook);
+            if let Err(e) = save_manifest(dir, &manifest) {
+                eprintln!("[worker] Error saving manifest: {:?}", e);
+            }
+        }
+    }
+}
+
+fn run_verify(dir: &Path) -> Result<(), Box<dyn std::error::Error>> {
+    println!("[verify] Checking notebook in {:?}", dir);
+
+    // 1. Bereinige eventuelle verwaiste .tmp-Dateien
+    let _ = cleanup_orphaned_temp_files(dir, Duration::from_secs(0));
+
+    // Prüfe, ob das Verzeichnis noch gar kein Notizbuch enthält (Prozess vor erstem Flush getötet)
+    let manifest_path = dir.join("manifest.json");
+    let manifest_bak = dir.join("manifest.json.bak");
+    if !manifest_path.exists() && !manifest_bak.exists() {
+        println!("[verify] Notebook not yet created on disk (killed prior to first save). Valid empty state.");
+        return Ok(());
+    }
+
+    // 2. Notizbuch laden
+    let (_notebook, manifest) = match load_notebook(dir) {
+        Ok(res) => res,
+        Err(e) => {
+            eprintln!("[verify] FAILED to load notebook: {:?}", e);
+            return Err(Box::new(e));
+        }
+    };
+
+    println!(
+        "[verify] Manifest loaded successfully: title='{}', pages={}, next_stroke_id={}",
+        manifest.title,
+        manifest.pages.len(),
+        manifest.next_stroke_id
+    );
+
+    // 3. Alle im Manifest registrierten Seiten laden und prüfen
+    for page_meta in &manifest.pages {
+        match load_page(dir, page_meta.id) {
+            Ok(page_data) => {
+                let page = page_data.to_page();
+                println!(
+                    "[verify] Page {} verified: {} strokes, background={:?}",
+                    page_meta.id,
+                    page.strokes.len(),
+                    page.background
+                );
+            }
+            Err(e) => {
+                eprintln!(
+                    "[verify] FAILED to load page {} referenced by manifest: {:?}",
+                    page_meta.id, e
+                );
+                return Err(Box::new(e));
+            }
+        }
+    }
+
+    // 4. Prüfen ob Quarantäne-Dateien existieren
+    if let Ok(entries) = std::fs::read_dir(dir) {
+        for entry in entries.flatten() {
+            let file_name = entry.file_name();
+            let name = file_name.to_string_lossy();
+            if name.contains(".corrupt-") {
+                println!("[verify] Notice: Found quarantined file: {}", name);
+            }
+        }
+    }
+
+    println!("[verify] SUCCESS: All pages and manifest are fully consistent!");
+    Ok(())
+}
+
+fn main() {
+    let args: Vec<String> = env::args().collect();
+    if args.len() < 3 {
+        eprintln!("Usage: crash_sim <init|worker|verify> <notebook_dir>");
+        process::exit(2);
+    }
+
+    let command = &args[1];
+    let notebook_dir = Path::new(&args[2]);
+
+    match command.as_str() {
+        "init" => match run_init(notebook_dir) {
+            Ok(_) => process::exit(0),
+            Err(e) => {
+                eprintln!("[init] Error: {}", e);
+                process::exit(1);
+            }
+        },
+        "worker" => {
+            run_worker(notebook_dir);
+        }
+        "verify" => match run_verify(notebook_dir) {
+            Ok(_) => process::exit(0),
+            Err(e) => {
+                eprintln!("[verify] Error: {}", e);
+                process::exit(1);
+            }
+        },
+        other => {
+            eprintln!("Unknown command: {}", other);
+            process::exit(2);
+        }
+    }
+}

src/canvas.rs

@@ -104,6 +104,8 @@ pub struct CanvasState {
     pub camera_buffer: wgpu::Buffer,
     pub camera_bind_group: wgpu::BindGroup,
     pub current_ink_color: [f32; 4],
+    pub current_stroke_width_mm: f32,
+    pub current_tool: crate::document::StrokeTool,
 
     // Statische Hintergrund-Geometrie
     pub paper_buffer: wgpu::Buffer,
@@ -374,6 +376,8 @@ impl CanvasState {
             camera_buffer,
             camera_bind_group,
             current_ink_color: default_ink_color,
+            current_stroke_width_mm: 0.5,
+            current_tool: crate::document::StrokeTool::Pen,
             paper_buffer,
             background_buffer,
             background_vertex_capacity: Self::INITIAL_BACKGROUND_CAPACITY,
@@ -502,10 +506,14 @@ impl CanvasState {
 
     /// Konfiguriert die Strichbreite in Millimetern.
     pub fn set_stroke_width_mm(&mut self, width_mm: f32) {
-        // 10 Einheiten = 1 mm. Radius = (width_mm * 10.0) / 2.0 = width_mm * 5.0.
-        let base_radius = (width_mm * 5.0).max(0.25);
-        self.spline_config.min_radius = (base_radius * 0.5).max(0.15);
-        self.spline_config.max_radius = (base_radius * 1.5).max(0.35);
+        self.current_stroke_width_mm = width_mm;
+        self.spline_config =
+            SplineConfig::from_width_units(width_mm * crate::document::UNITS_PER_MM);
+    }
+
+    /// Setzt das aktive Zeichenwerkzeug für den Stift.
+    pub fn set_tool(&mut self, tool: crate::document::StrokeTool) {
+        self.current_tool = tool;
     }
 
     /// Setzt den Seitenhintergrund und aktualisiert bei Bedarf den Vertex-Puffer.
@@ -643,6 +651,10 @@ impl CanvasState {
             self.current_ink_color,
             &self.spline_config,
         );
+        let mut stroke = stroke;
+        stroke.tool = self.current_tool;
+        stroke.width = self.current_stroke_width_mm * crate::document::UNITS_PER_MM;
+        stroke.finalized = true;
 
         // Temporären GPU-Live-Buffer vollständig leeren
         self.live_samples.clear();

src/document.rs

@@ -103,6 +103,16 @@ pub fn point_to_segment_distance(p: glam::Vec2, a: glam::Vec2, b: glam::Vec2) ->
     (p - projection).length()
 }
 
+/// Das Werkzeug, mit dem ein Strich gezeichnet wurde.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default, serde::Serialize, serde::Deserialize)]
+#[serde(rename_all = "lowercase")]
+pub enum StrokeTool {
+    #[default]
+    Pen,
+    Highlighter,
+    Shape,
+}
+
 /// Ein einzelner Vektor-Strich auf einer Seite.
 #[derive(Debug, Clone, PartialEq)]
 pub struct Stroke {
@@ -112,6 +122,9 @@ pub struct Stroke {
     pub aabb: Aabb,
     pub color: [f32; 4],
     pub shape: Option<crate::geometry::RecognizedShape>,
+    pub tool: StrokeTool,
+    pub width: f32,
+    pub finalized: bool,
 }
 
 impl Stroke {
@@ -141,6 +154,9 @@ impl Stroke {
             aabb,
             color,
             shape: None,
+            tool: StrokeTool::Pen,
+            width: 5.0,
+            finalized: true,
         }
     }
 
@@ -157,6 +173,22 @@ impl Stroke {
     /// Verknüpft diesen Strich mit einer mathematisch erkannten Form.
     pub fn with_shape(mut self, shape: crate::geometry::RecognizedShape) -> Self {
         self.shape = Some(shape);
+        self.tool = StrokeTool::Shape;
+        self
+    }
+
+    pub fn with_tool(mut self, tool: StrokeTool) -> Self {
+        self.tool = tool;
+        self
+    }
+
+    pub fn with_width(mut self, width: f32) -> Self {
+        self.width = width;
+        self
+    }
+
+    pub fn with_finalized(mut self, finalized: bool) -> Self {
+        self.finalized = finalized;
         self
     }
 
@@ -304,6 +336,22 @@ pub enum PageBackground {
     DotGrid,
 }
 
+/// Persistenzstatus einer Seite zum Schutz vor unbeabsichtigtem Überschreiben bei Ladefehlern.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
+pub enum PersistState {
+    #[default]
+    Normal,
+    ReadOnlyAfterLoadError,
+}
+
+/// Warnung beim Laden einer Seite (beschädigte Datei oder I/O-Fehler).
+#[derive(Debug, Clone, PartialEq)]
+pub struct PageLoadWarning {
+    pub page_id: u64,
+    pub message: String,
+    pub quarantine_path: Option<std::path::PathBuf>,
+}
+
 /// Eine einzelne Notizbuchseite mit Strichen, Hintergrund und gecachten Meshes.
 #[derive(Debug, Clone)]
 pub struct Page {
@@ -314,9 +362,7 @@ pub struct Page {
     pub stroke_ranges: Vec<Range<u32>>,
     pub is_dirty: bool,
     pub is_loaded: bool,
-    /// Laden von der Festplatte ist fehlgeschlagen; die Seite ist ein leerer Ersatz und
-    /// darf niemals gespeichert werden, damit die Originaldatei nicht überschrieben wird.
-    pub load_failed: bool,
+    pub persist: PersistState,
     pub history: HistoryStack,
 }
 
@@ -330,7 +376,7 @@ impl Page {
             stroke_ranges: Vec::new(),
             is_dirty: false,
             is_loaded: true,
-            load_failed: false,
+            persist: PersistState::Normal,
             history: HistoryStack::new(),
         }
     }
@@ -345,11 +391,19 @@ impl Page {
             stroke_ranges: Vec::new(),
             is_dirty: false,
             is_loaded: false,
-            load_failed: false,
+            persist: PersistState::Normal,
             history: HistoryStack::new(),
         }
     }
 
+    pub fn is_readonly(&self) -> bool {
+        self.persist == PersistState::ReadOnlyAfterLoadError
+    }
+
+    pub fn unlock_after_load_error(&mut self) {
+        self.persist = PersistState::Normal;
+    }
+
     /// Fügt einen neuen Strich hinzu und registriert ihn im History-Stack.
     pub fn add_stroke(&mut self, stroke: Stroke) {
         self.history.push(HistoryAction::AddStroke(stroke.clone()));
@@ -592,6 +646,7 @@ pub struct Notebook {
     pub current_page_index: usize,
     pub next_stroke_id: u64,
     pub next_page_id: u64,
+    pub load_warnings: std::collections::HashMap<u64, PageLoadWarning>,
 }
 
 impl Notebook {
@@ -601,6 +656,7 @@ impl Notebook {
             current_page_index: 0,
             next_stroke_id: 1,
             next_page_id: 1,
+            load_warnings: std::collections::HashMap::new(),
         };
         // Erste Standardseite anlegen (5mm Grid)
         nb.add_page(PageBackground::Grid5mm);
@@ -619,6 +675,7 @@ impl Notebook {
             current_page_index,
             next_stroke_id,
             next_page_id,
+            load_warnings: std::collections::HashMap::new(),
         };
         if nb.pages.is_empty() {
             nb.add_page(PageBackground::Grid5mm);

src/export.rs

@@ -140,11 +140,9 @@ pub fn generate_pdf_document(
         return Err("Notizbuch enthält keine Seiten".into());
     }
     // Nicht geladene Seiten würden sonst stillschweigend als leere Seiten exportiert
-    if let Some(page) = notebook
-        .pages
-        .iter()
-        .find(|p| !p.is_loaded || p.load_failed)
-    {
+    if let Some(page) = notebook.pages.iter().find(|p| {
+        !p.is_loaded || p.persist == crate::document::PersistState::ReadOnlyAfterLoadError
+    }) {
         return Err(format!(
             "Seite {} ist nicht geladen – Export abgebrochen (vorher storage::load_all_pages aufrufen)",
             page.id

src/geometry.rs

@@ -1411,6 +1411,9 @@ pub fn shape_to_stroke(
     let (samples, vertices) = shape_to_mesh(&shape, width_units, color);
     let mut stroke = Stroke::new(stroke_id, samples, vertices, color);
     stroke.shape = Some(shape);
+    stroke.width = width_units;
+    stroke.tool = crate::document::StrokeTool::Shape;
+    stroke.finalized = true;
     stroke
 }
 

src/main.rs

@@ -159,9 +159,17 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
 
     // 1. Notizbuch aus Storage laden oder initialisieren (Session-Wiederherstellung)
     let storage_base_dir = storage::default_storage_dir();
+    let _ = storage::cleanup_trash(
+        &storage_base_dir,
+        std::time::Duration::from_secs(30 * 24 * 3600),
+    );
     let available_notebooks = storage::list_notebooks(&storage_base_dir);
 
-    let (initial_id, initial_title) = if let Some(first) = available_notebooks.first() {
+    // Beschädigte Notizbücher nicht automatisch öffnen
+    let (initial_id, initial_title) = if let Some(first) = available_notebooks
+        .iter()
+        .find(|s| s.status == storage::NotebookStatus::Normal)
+    {
         (first.id.clone(), first.title.clone())
     } else {
         ("default".to_string(), "Standard-Notizbuch".to_string())
@@ -231,6 +239,24 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
     }
     let mut selection_state = SelectionState::new();
 
+    let mut _notebook_lock = match storage::NotebookLock::acquire(&storage_dir) {
+        Ok(lock) => {
+            autosave.set_read_only(false);
+            Some(lock)
+        }
+        Err(storage::StorageError::AlreadyLocked(msg)) => {
+            eprintln!("[Storage-Lock] {msg}");
+            autosave.set_read_only(true);
+            ui_state.set_export_message("⚠️ In anderer Instanz geöffnet (Schreibschutz)");
+            None
+        }
+        Err(e) => {
+            eprintln!("[Storage-Lock] Konnte Lock nicht erwerben: {e}");
+            autosave.set_read_only(true);
+            None
+        }
+    };
+
     // Initiale Seite und Werkzeugeinstellungen mit Canvas synchronisieren
     canvas.sync_page(notebook.current_page_mut());
     canvas.set_stroke_color(ui_state.pen_color);
@@ -410,7 +436,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                                 );
                                                 if !removed.is_empty() {
                                                     canvas.sync_page(page);
-                                                    autosave.mark_dirty(&notebook, &manifest);
+                                                    autosave.mark_dirty(&notebook, &mut manifest);
                                                     update_window_title(
                                                         &window,
                                                         &notebook,
@@ -487,7 +513,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                                 );
                                                 if !removed.is_empty() {
                                                     canvas.sync_page(page);
-                                                    autosave.mark_dirty(&notebook, &manifest);
+                                                    autosave.mark_dirty(&notebook, &mut manifest);
                                                     update_window_title(
                                                         &window,
                                                         &notebook,
@@ -638,8 +664,16 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                 match event {
                     WindowEvent::CloseRequested => {
                         println!("[Shutdown] Sichere alle ungespeicherten Daten auf Festplatte...");
-                        autosave.shutdown();
-                        target.exit();
+                        match autosave.shutdown() {
+                            Ok(()) => {
+                                target.exit();
+                            }
+                            Err(err) => {
+                                eprintln!("[Shutdown-Fehler] Konnte nicht geordnet beenden: {err}");
+                                ui_state.shutdown_error = Some(err);
+                                window.request_redraw();
+                            }
+                        }
                     }
 
                     WindowEvent::Focused(false) => {
@@ -708,7 +742,10 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                         match &logical_key {
                             Key::Named(NamedKey::Escape) => {
                                 let mut changed = false;
-                                if ui_state.is_pen_menu_open
+                                if ui_state.shutdown_error.is_some() {
+                                    ui_state.shutdown_error = None;
+                                    changed = true;
+                                } else if ui_state.is_pen_menu_open
                                     || ui_state.is_highlighter_menu_open
                                     || ui_state.show_page_jump_popup
                                     || ui_state.is_document_menu_open
@@ -737,7 +774,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                 if notebook.current_page_mut().undo() {
                                     selection_state.clear();
                                     canvas.sync_page(notebook.current_page_mut());
-                                    autosave.mark_dirty(&notebook, &manifest);
+                                    autosave.mark_dirty(&notebook, &mut manifest);
                                     update_window_title(&window, &notebook, &manifest, ui_state.active_tool, autosave.status());
                                     window.request_redraw();
                                 }
@@ -751,7 +788,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                 if notebook.current_page_mut().redo() {
                                     selection_state.clear();
                                     canvas.sync_page(notebook.current_page_mut());
-                                    autosave.mark_dirty(&notebook, &manifest);
+                                    autosave.mark_dirty(&notebook, &mut manifest);
                                     update_window_title(&window, &notebook, &manifest, ui_state.active_tool, autosave.status());
                                     window.request_redraw();
                                 }
@@ -781,7 +818,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                 if !new_ids.is_empty() {
                                     canvas.sync_page(notebook.current_page_mut());
                                     manifest.next_stroke_id = notebook.next_stroke_id;
-                                    autosave.mark_dirty(&notebook, &manifest);
+                                    autosave.mark_dirty(&notebook, &mut manifest);
                                     ui_state.set_export_message(format!("{} Objekt(e) eingefügt", new_ids.len()));
                                     window.request_redraw();
                                 }
@@ -793,7 +830,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                     let removed = selection_state.delete_selected(notebook.current_page_mut());
                                     if !removed.is_empty() {
                                         canvas.sync_page(notebook.current_page_mut());
-                                        autosave.mark_dirty(&notebook, &manifest);
+                                        autosave.mark_dirty(&notebook, &mut manifest);
                                         ui_state.set_export_message(format!("{} Objekt(e) gelöscht", removed.len()));
                                         window.request_redraw();
                                     }
@@ -802,9 +839,16 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
 
                             // Jetzt speichern (Disk Flush): Strg + S
                             Key::Character(c) if c.eq_ignore_ascii_case("s") && ctrl => {
-                                match autosave.save_now(&notebook, &manifest) {
-                                    Ok(()) => ui_state.set_export_message("Gespeichert"),
-                                    Err(err) => ui_state.set_export_message(format!("Speichern fehlgeschlagen: {err}")),
+                                match autosave.flush() {
+                                    Ok(()) => {
+                                        ui_state.set_export_message("Gespeichert");
+                                    }
+                                    Err(err) => {
+                                        ui_state.set_export_message(format!(
+                                            "Speicherfehler: {}",
+                                            err.messages.join(", ")
+                                        ));
+                                    }
                                 }
                                 update_window_title(
                                     &window,
@@ -855,7 +899,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                     let color = [0.12, 0.12, 0.14, 1.0];
                                     if selection_state.recolor_selected(notebook.current_page_mut(), color) {
                                         canvas.sync_page(notebook.current_page_mut());
-                                        autosave.mark_dirty(&notebook, &manifest);
+                                        autosave.mark_dirty(&notebook, &mut manifest);
                                         ui_state.set_export_message("Auswahl auf Schwarz umgefärbt".to_string());
                                         window.request_redraw();
                                     }
@@ -875,7 +919,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                     let color = [0.15, 0.35, 0.85, 1.0];
                                     if selection_state.recolor_selected(notebook.current_page_mut(), color) {
                                         canvas.sync_page(notebook.current_page_mut());
-                                        autosave.mark_dirty(&notebook, &manifest);
+                                        autosave.mark_dirty(&notebook, &mut manifest);
                                         ui_state.set_export_message("Auswahl auf Blau umgefärbt".to_string());
                                         window.request_redraw();
                                     }
@@ -894,7 +938,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                 if !selection_state.is_empty() {
                                     if selection_state.rotate_selected_90_deg(notebook.current_page_mut()) {
                                         canvas.sync_page(notebook.current_page_mut());
-                                        autosave.mark_dirty(&notebook, &manifest);
+                                        autosave.mark_dirty(&notebook, &mut manifest);
                                         ui_state.set_export_message("Auswahl um 90° gedreht".to_string());
                                         window.request_redraw();
                                     }
@@ -918,7 +962,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                     PageBackground::Blank => PageBackground::Grid5mm,
                                 };
                                 canvas.sync_page(page);
-                                autosave.mark_dirty(&notebook, &manifest);
+                                autosave.mark_dirty(&notebook, &mut manifest);
                                 update_window_title(&window, &notebook, &manifest, ui_state.active_tool, autosave.status());
                                 window.request_redraw();
                             }
@@ -932,7 +976,9 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                 canvas.sync_page(notebook.current_page_mut());
                                 manifest.current_page_index = notebook.current_page_index;
                                 manifest.next_page_id = notebook.next_page_id;
-                                autosave.mark_dirty(&notebook, &manifest);
+                                manifest.sync_from_notebook(&notebook);
+                                autosave.mark_manifest_dirty(&manifest);
+                                autosave.mark_dirty(&notebook, &mut manifest);
                                 update_window_title(&window, &notebook, &manifest, ui_state.active_tool, autosave.status());
                                 window.request_redraw();
                             }
@@ -944,7 +990,9 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                 canvas.sync_page(notebook.current_page_mut());
                                 manifest.current_page_index = notebook.current_page_index;
                                 manifest.next_page_id = notebook.next_page_id;
-                                autosave.mark_dirty(&notebook, &manifest);
+                                manifest.sync_from_notebook(&notebook);
+                                autosave.mark_manifest_dirty(&manifest);
+                                autosave.mark_dirty(&notebook, &mut manifest);
                                 update_window_title(&window, &notebook, &manifest, ui_state.active_tool, autosave.status());
                                 window.request_redraw();
                             }
@@ -957,7 +1005,9 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                 let _ = storage::ensure_page_loaded(&storage_dir, &mut notebook, curr);
                                 canvas.sync_page(notebook.current_page_mut());
                                 manifest.current_page_index = notebook.current_page_index;
-                                autosave.mark_dirty(&notebook, &manifest);
+                                manifest.sync_from_notebook(&notebook);
+                                autosave.mark_manifest_dirty(&manifest);
+                                autosave.mark_dirty(&notebook, &mut manifest);
                                 update_window_title(&window, &notebook, &manifest, ui_state.active_tool, autosave.status());
                                 window.request_redraw();
                             }
@@ -970,7 +1020,9 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                 let _ = storage::ensure_page_loaded(&storage_dir, &mut notebook, curr);
                                 canvas.sync_page(notebook.current_page_mut());
                                 manifest.current_page_index = notebook.current_page_index;
-                                autosave.mark_dirty(&notebook, &manifest);
+                                manifest.sync_from_notebook(&notebook);
+                                autosave.mark_manifest_dirty(&manifest);
+                                autosave.mark_dirty(&notebook, &mut manifest);
                                 update_window_title(&window, &notebook, &manifest, ui_state.active_tool, autosave.status());
                                 window.request_redraw();
                             }
@@ -983,7 +1035,9 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                 let _ = storage::ensure_page_loaded(&storage_dir, &mut notebook, curr);
                                 canvas.sync_page(notebook.current_page_mut());
                                 manifest.current_page_index = notebook.current_page_index;
-                                autosave.mark_dirty(&notebook, &manifest);
+                                manifest.sync_from_notebook(&notebook);
+                                autosave.mark_manifest_dirty(&manifest);
+                                autosave.mark_dirty(&notebook, &mut manifest);
                                 update_window_title(&window, &notebook, &manifest, ui_state.active_tool, autosave.status());
                                 window.request_redraw();
                             }
@@ -1023,8 +1077,16 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                             // Beenden: Strg + Q
                             Key::Character(c) if c.eq_ignore_ascii_case("q") && ctrl => {
                                 println!("[Shutdown] Sichere alle ungespeicherten Daten auf Festplatte...");
-                                autosave.shutdown();
-                                target.exit();
+                                match autosave.shutdown() {
+                                    Ok(()) => {
+                                        target.exit();
+                                    }
+                                    Err(err) => {
+                                        eprintln!("[Shutdown-Fehler] Konnte nicht geordnet beenden: {err}");
+                                        ui_state.shutdown_error = Some(err);
+                                        window.request_redraw();
+                                    }
+                                }
                             }
 
 
@@ -1064,7 +1126,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                         let removed = page.erase_at(page_pt, eraser_radius, stroke_max_radius);
                                         if !removed.is_empty() {
                                             canvas.sync_page(page);
-                                            autosave.mark_dirty(&notebook, &manifest);
+                                            autosave.mark_dirty(&notebook, &mut manifest);
                                             update_window_title(&window, &notebook, &manifest, ui_state.active_tool, autosave.status());
                                             window.request_redraw();
                                         }
@@ -1162,7 +1224,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                                     let new_stroke = geometry::shape_to_stroke(shape, old_id, stroke_color, stroke_width);
                                                     notebook.current_page_mut().replace_stroke(old_id, new_stroke);
                                                     canvas.sync_page(notebook.current_page_mut());
-                                                    autosave.mark_dirty(&notebook, &manifest);
+                                                    autosave.mark_dirty(&notebook, &mut manifest);
                                                     ui_state.set_export_message(format!("{shape_name} ausgerichtet! (Undo mit Strg+Z)"));
                                                     window.request_redraw();
                                                     return;
@@ -1219,7 +1281,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                             let final_strokes = notebook.current_page().get_strokes(&selection_state.selected_ids);
                                             if !initial_strokes.is_empty() && !final_strokes.is_empty() && initial_strokes != final_strokes {
                                                 notebook.current_page_mut().commit_modified_strokes(initial_strokes, final_strokes);
-                                                autosave.mark_dirty(&notebook, &manifest);
+                                                autosave.mark_dirty(&notebook, &mut manifest);
                                             }
                                             window.request_redraw();
                                         }
@@ -1332,7 +1394,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                     let removed = page.erase_at(page_pt, eraser_radius, stroke_max_radius);
                                     if !removed.is_empty() {
                                         canvas.sync_page(page);
-                                        autosave.mark_dirty(&notebook, &manifest);
+                                        autosave.mark_dirty(&notebook, &mut manifest);
                                         update_window_title(&window, &notebook, &manifest, ui_state.active_tool, autosave.status());
                                         window.request_redraw();
                                     }
@@ -1456,7 +1518,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                                 let removed = page.erase_at(page_pt, eraser_radius, stroke_max_radius);
                                                 if !removed.is_empty() {
                                                     canvas.sync_page(page);
-                                                    autosave.mark_dirty(&notebook, &manifest);
+                                                    autosave.mark_dirty(&notebook, &mut manifest);
                                                     update_window_title(&window, &notebook, &manifest, ui_state.active_tool, autosave.status());
                                                     window.request_redraw();
                                                 }
@@ -1597,7 +1659,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                             let removed = page.erase_at(page_pt, eraser_radius, stroke_max_radius);
                                             if !removed.is_empty() {
                                                 canvas.sync_page(page);
-                                                autosave.mark_dirty(&notebook, &manifest);
+                                                autosave.mark_dirty(&notebook, &mut manifest);
                                                 update_window_title(&window, &notebook, &manifest, ui_state.active_tool, autosave.status());
                                                 window.request_redraw();
                                             }
@@ -1688,7 +1750,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                                 let final_strokes = notebook.current_page().get_strokes(&selection_state.selected_ids);
                                                 if !initial_strokes.is_empty() && !final_strokes.is_empty() && initial_strokes != final_strokes {
                                                     notebook.current_page_mut().commit_modified_strokes(initial_strokes, final_strokes);
-                                                    autosave.mark_dirty(&notebook, &manifest);
+                                                    autosave.mark_dirty(&notebook, &mut manifest);
                                                 }
                                                 window.request_redraw();
                                             }
@@ -1772,7 +1834,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                     if !selection_state.is_empty()
                                         && selection_state.recolor_selected(notebook.current_page_mut(), color) {
                                             canvas.sync_page(notebook.current_page_mut());
-                                            autosave.mark_dirty(&notebook, &manifest);
+                                            autosave.mark_dirty(&notebook, &mut manifest);
                                             ui_state.set_export_message("Auswahl umgefärbt".to_string());
                                         }
                                     match ui_state.active_tool {
@@ -1807,7 +1869,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                         let removed = selection_state.delete_selected(notebook.current_page_mut());
                                         if !removed.is_empty() {
                                             canvas.sync_page(notebook.current_page_mut());
-                                            autosave.mark_dirty(&notebook, &manifest);
+                                            autosave.mark_dirty(&notebook, &mut manifest);
                                             ui_state.set_export_message(format!("{} Objekt(e) gelöscht", removed.len()));
                                             window.request_redraw();
                                         }
@@ -1834,7 +1896,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                     if !new_ids.is_empty() {
                                         canvas.sync_page(notebook.current_page_mut());
                                         manifest.next_stroke_id = notebook.next_stroke_id;
-                                        autosave.mark_dirty(&notebook, &manifest);
+                                        autosave.mark_dirty(&notebook, &mut manifest);
                                         ui_state.set_export_message(format!("{} Objekt(e) eingefügt", new_ids.len()));
                                         window.request_redraw();
                                     }
@@ -1843,7 +1905,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                     if !selection_state.is_empty()
                                         && selection_state.rotate_selected_90_deg(notebook.current_page_mut()) {
                                             canvas.sync_page(notebook.current_page_mut());
-                                            autosave.mark_dirty(&notebook, &manifest);
+                                            autosave.mark_dirty(&notebook, &mut manifest);
                                             ui_state.set_export_message("Auswahl um 90° gedreht".to_string());
                                             window.request_redraw();
                                         }
@@ -1871,7 +1933,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                     if notebook.current_page_mut().undo() {
                                         selection_state.clear();
                                         canvas.sync_page(notebook.current_page_mut());
-                                        autosave.mark_dirty(&notebook, &manifest);
+                                        autosave.mark_dirty(&notebook, &mut manifest);
                                         update_window_title(&window, &notebook, &manifest, ui_state.active_tool, autosave.status());
                                         window.request_redraw();
                                     }
@@ -1880,7 +1942,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                     if notebook.current_page_mut().redo() {
                                         selection_state.clear();
                                         canvas.sync_page(notebook.current_page_mut());
-                                        autosave.mark_dirty(&notebook, &manifest);
+                                        autosave.mark_dirty(&notebook, &mut manifest);
                                         update_window_title(&window, &notebook, &manifest, ui_state.active_tool, autosave.status());
                                         window.request_redraw();
                                     }
@@ -1892,7 +1954,9 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                     let _ = storage::ensure_page_loaded(&storage_dir, &mut notebook, curr);
                                     canvas.sync_page(notebook.current_page_mut());
                                     manifest.current_page_index = notebook.current_page_index;
-                                    autosave.mark_dirty(&notebook, &manifest);
+                                    manifest.sync_from_notebook(&notebook);
+                                    autosave.mark_manifest_dirty(&manifest);
+                                    autosave.mark_dirty(&notebook, &mut manifest);
                                     update_window_title(&window, &notebook, &manifest, ui_state.active_tool, autosave.status());
                                     window.request_redraw();
                                 }
@@ -1904,7 +1968,17 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                     canvas.sync_page(notebook.current_page_mut());
                                     manifest.current_page_index = notebook.current_page_index;
                                     manifest.next_page_id = notebook.next_page_id;
-                                    autosave.mark_dirty(&notebook, &manifest);
+                                    manifest.pages = notebook
+                                        .pages
+                                        .iter()
+                                        .map(|p| storage::PageMeta {
+                                            id: p.id,
+                                            background: Some(p.background),
+                                        })
+                                        .collect();
+                                    manifest.sync_from_notebook(&notebook);
+                                    autosave.mark_manifest_dirty(&manifest);
+                                    autosave.mark_dirty(&notebook, &mut manifest);
                                     update_window_title(&window, &notebook, &manifest, ui_state.active_tool, autosave.status());
                                     window.request_redraw();
                                 }
@@ -1914,8 +1988,18 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                     notebook.add_page(bg);
                                     manifest.current_page_index = notebook.current_page_index;
                                     manifest.next_page_id = notebook.next_page_id;
+                                    manifest.pages = notebook
+                                        .pages
+                                        .iter()
+                                        .map(|p| storage::PageMeta {
+                                            id: p.id,
+                                            background: Some(p.background),
+                                        })
+                                        .collect();
                                     canvas.sync_page(notebook.current_page_mut());
-                                    autosave.mark_dirty(&notebook, &manifest);
+                                    manifest.sync_from_notebook(&notebook);
+                                    autosave.mark_manifest_dirty(&manifest);
+                                    autosave.mark_dirty(&notebook, &mut manifest);
                                     update_window_title(&window, &notebook, &manifest, ui_state.active_tool, autosave.status());
                                     window.request_redraw();
                                 }
@@ -1926,7 +2010,9 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                         let _ = storage::ensure_page_loaded(&storage_dir, &mut notebook, idx);
                                         canvas.sync_page(notebook.current_page_mut());
                                         manifest.current_page_index = idx;
-                                        autosave.mark_dirty(&notebook, &manifest);
+                                        manifest.sync_from_notebook(&notebook);
+                                        autosave.mark_manifest_dirty(&manifest);
+                                        autosave.mark_dirty(&notebook, &mut manifest);
                                         update_window_title(&window, &notebook, &manifest, ui_state.active_tool, autosave.status());
                                         window.request_redraw();
                                     }
@@ -1935,7 +2021,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                     let page = notebook.current_page_mut();
                                     page.background = bg;
                                     canvas.sync_page(page);
-                                    autosave.mark_dirty(&notebook, &manifest);
+                                    autosave.mark_dirty(&notebook, &mut manifest);
                                     update_window_title(&window, &notebook, &manifest, ui_state.active_tool, autosave.status());
                                     window.request_redraw();
                                 }
@@ -1957,9 +2043,25 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                         let new_notebook_dir = storage_base_dir.join(&id);
                                         match storage::load_notebook(&new_notebook_dir) {
                                             Ok((loaded_nb, loaded_manifest)) => {
-                                                if let Err(err) = autosave.switch_notebook_dir(new_notebook_dir.clone()) {
-    eprintln!("[Autosave-Fehler] Vorheriges Notizbuch nicht vollständig gespeichert: {err}");
-}
+                                                let _ = autosave.flush();
+                                                match storage::NotebookLock::acquire(&new_notebook_dir) {
+                                                    Ok(lock) => {
+                                                        _notebook_lock = Some(lock);
+                                                        autosave.set_read_only(false);
+                                                    }
+                                                    Err(storage::StorageError::AlreadyLocked(msg)) => {
+                                                        eprintln!("[Storage-Lock] {msg}");
+                                                        _notebook_lock = None;
+                                                        autosave.set_read_only(true);
+                                                        ui_state.set_export_message("⚠️ In anderer Instanz geöffnet (Schreibschutz)");
+                                                    }
+                                                    Err(e) => {
+                                                        eprintln!("[Storage-Lock] Konnte Lock nicht erwerben: {e}");
+                                                        _notebook_lock = None;
+                                                        autosave.set_read_only(true);
+                                                    }
+                                                }
+                                                autosave.switch_notebook_dir(new_notebook_dir.clone());
                                                 notebook = loaded_nb;
                                                 manifest = loaded_manifest;
                                                 storage_dir = new_notebook_dir;
@@ -1970,7 +2072,9 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                                 ui_state.is_document_menu_open = false;
                                                 canvas.sync_page(notebook.current_page_mut());
                                                 update_window_title(&window, &notebook, &manifest, ui_state.active_tool, autosave.status());
-                                                ui_state.set_export_message(format!("Dokument '{}' geöffnet", manifest.title));
+                                                if _notebook_lock.is_some() {
+                                                    ui_state.set_export_message(format!("Dokument '{}' geöffnet", manifest.title));
+                                                }
                                                 window.request_redraw();
                                             }
                                             Err(err) => {
@@ -1981,11 +2085,12 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                     }
                                 }
                                 UiAction::CreateNotebook(title) => {
+                                    let _ = autosave.flush();
                                     match storage::create_new_notebook(&storage_base_dir, &title) {
                                         Ok((new_nb, new_manifest, new_dir)) => {
-                                            if let Err(err) = autosave.switch_notebook_dir(new_dir.clone()) {
-    eprintln!("[Autosave-Fehler] Vorheriges Notizbuch nicht vollständig gespeichert: {err}");
-}
+                                            _notebook_lock = storage::NotebookLock::acquire(&new_dir).ok();
+                                            autosave.set_read_only(_notebook_lock.is_none());
+                                            autosave.switch_notebook_dir(new_dir.clone());
                                             notebook = new_nb;
                                             manifest = new_manifest;
                                             storage_dir = new_dir;
@@ -2012,6 +2117,8 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                             Ok(()) => {
                                                 ui_state.document_title = manifest.title.clone();
                                                 ui_state.available_notebooks = storage::list_notebooks(&storage_base_dir);
+                                                manifest.sync_from_notebook(&notebook);
+                                                autosave.mark_manifest_dirty(&manifest);
                                                 update_window_title(&window, &notebook, &manifest, ui_state.active_tool, autosave.status());
                                                 ui_state.set_export_message(format!("Umbenannt in '{}'", new_title));
                                                 window.request_redraw();
@@ -2036,54 +2143,66 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                 UiAction::DeleteNotebook(id) => {
                                     let target_dir = storage_base_dir.join(&id);
                                     let is_current = id == manifest.id;
+                                    let deleted_title = ui_state
+                                        .available_notebooks
+                                        .iter()
+                                        .find(|s| s.id == id)
+                                        .map(|s| s.title.clone())
+                                        .unwrap_or_else(|| id.clone());
+
                                     if is_current {
-                                        // Ausstehende Autosave-Schreibvorgänge VOR dem Löschen abarbeiten,
-                                        // sonst legen sie den gelöschten Ordner danach wieder an.
                                         let _ = autosave.flush();
+                                        drop(_notebook_lock.take());
                                     }
-                                    match storage::delete_notebook(&target_dir) {
-                                        Ok(()) => {
+
+                                    match storage::delete_notebook(&target_dir, &storage_base_dir) {
+                                        Ok(trash_path) => {
+                                            ui_state.last_deleted_notebook = Some((trash_path, deleted_title));
                                             ui_state.available_notebooks = storage::list_notebooks(&storage_base_dir);
                                             if is_current {
-                                                // Erstes ladbares Notizbuch öffnen, sonst ein neues anlegen
-                                                let replacement = ui_state
+                                                if let Some(first) = ui_state
                                                     .available_notebooks
                                                     .iter()
-                                                    .find_map(|summary| {
-                                                        let dir = storage_base_dir.join(&summary.id);
-                                                        match storage::load_notebook(&dir) {
-                                                            Ok((nb, m)) => Some((nb, m, dir)),
-                                                            Err(err) => {
-                                                                eprintln!("[Dokument-Fehler] Konnte Dokument '{}' nicht laden: {err}", summary.id);
-                                                                None
-                                                            }
+                                                    .find(|s| s.status != storage::NotebookStatus::Damaged)
+                                                    .cloned()
+                                                {
+                                                    let new_notebook_dir = storage_base_dir.join(&first.id);
+                                                    match storage::load_notebook(&new_notebook_dir) {
+                                                        Ok((loaded_nb, loaded_manifest)) => {
+                                                            _notebook_lock = storage::NotebookLock::acquire(&new_notebook_dir).ok();
+                                                            autosave.set_read_only(_notebook_lock.is_none());
+                                                            autosave.switch_notebook_dir(new_notebook_dir.clone());
+                                                            notebook = loaded_nb;
+                                                            manifest = loaded_manifest;
+                                                            storage_dir = new_notebook_dir;
+                                                            selection_state.clear();
+                                                            ui_state.current_notebook_id = manifest.id.clone();
+                                                            ui_state.document_title = manifest.title.clone();
+                                                            canvas.sync_page(notebook.current_page_mut());
+                                                            update_window_title(&window, &notebook, &manifest, ui_state.active_tool, autosave.status());
+                                                            ui_state.set_export_message(format!("Gewechselt zu '{}'", manifest.title));
                                                         }
-                                                    })
-                                                    .map(Ok)
-                                                    .unwrap_or_else(|| storage::create_new_notebook(&storage_base_dir, "Standard-Notizbuch"));
-                                                match replacement {
-                                                    Ok((new_nb, new_manifest, new_dir)) => {
-                                                        if let Err(err) = autosave.switch_notebook_dir(new_dir.clone()) {
-                                                            eprintln!("[Autosave-Fehler] Vorheriges Notizbuch nicht vollständig gespeichert: {err}");
+                                                        Err(err) => {
+                                                            eprintln!("[Dokument-Fehler] Konnte Dokument '{}' nicht laden: {err}", first.id);
                                                         }
-                                                        notebook = new_nb;
-                                                        manifest = new_manifest;
-                                                        storage_dir = new_dir;
-                                                        selection_state.clear();
-                                                        ui_state.current_notebook_id = manifest.id.clone();
-                                                        ui_state.document_title = manifest.title.clone();
-                                                        ui_state.available_notebooks = storage::list_notebooks(&storage_base_dir);
-                                                        canvas.sync_page(notebook.current_page_mut());
-                                                        update_window_title(&window, &notebook, &manifest, ui_state.active_tool, autosave.status());
-                                                        ui_state.set_export_message(format!("Gewechselt zu '{}'", manifest.title));
-                                                    }
-                                                    Err(err) => {
-                                                        eprintln!("[Dokument-Fehler] Konnte kein Ersatz-Notizbuch anlegen: {err}");
-                                                        ui_state.set_export_message(format!("Dokument gelöscht, aber kein Ersatz-Notizbuch: {err}"));
                                                     }
+                                                } else if let Ok((new_nb, new_manifest, new_dir)) = storage::create_new_notebook(&storage_base_dir, "Standard-Notizbuch") {
+                                                    _notebook_lock = storage::NotebookLock::acquire(&new_dir).ok();
+                                                    autosave.set_read_only(_notebook_lock.is_none());
+                                                    autosave.switch_notebook_dir(new_dir.clone());
+                                                    notebook = new_nb;
+                                                    manifest = new_manifest;
+                                                    storage_dir = new_dir;
+                                                    selection_state.clear();
+                                                    ui_state.current_notebook_id = manifest.id.clone();
+                                                    ui_state.document_title = manifest.title.clone();
+                                                    ui_state.available_notebooks = storage::list_notebooks(&storage_base_dir);
+                                                    canvas.sync_page(notebook.current_page_mut());
+                                                    update_window_title(&window, &notebook, &manifest, ui_state.active_tool, autosave.status());
+                                                    ui_state.set_export_message("Standard-Notizbuch erstellt".to_string());
                                                 }
                                             } else {
-                                                ui_state.set_export_message("Dokument gelöscht".to_string());
+                                                ui_state.set_export_message("Dokument in Papierkorb verschoben".to_string());
                                             }
                                             window.request_redraw();
                                         }
@@ -2093,6 +2212,40 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                         }
                                     }
                                 }
+                                UiAction::UndoDeleteNotebook => {
+                                    if let Some((trash_path, _title)) = ui_state.last_deleted_notebook.take() {
+                                        match storage::restore_notebook_from_trash(&storage_base_dir, &trash_path) {
+                                            Ok(_restored_dir) => {
+                                                ui_state.available_notebooks = storage::list_notebooks(&storage_base_dir);
+                                                ui_state.set_export_message("Notizbuch wiederhergestellt".to_string());
+                                                window.request_redraw();
+                                            }
+                                            Err(err) => {
+                                                eprintln!("[Dokument-Fehler] Konnte Notizbuch nicht wiederherstellen: {err}");
+                                                ui_state.set_export_message(format!("Fehler beim Wiederherstellen: {err}"));
+                                            }
+                                        }
+                                    }
+                                }
+                                UiAction::RestoreNotebookBackup(id) => {
+                                    let target_dir = storage_base_dir.join(&id);
+                                    match storage::restore_manifest_from_backup(&target_dir) {
+                                        Ok(()) => {
+                                            ui_state.available_notebooks = storage::list_notebooks(&storage_base_dir);
+                                            ui_state.set_export_message("Manifest aus Backup wiederhergestellt".to_string());
+                                            window.request_redraw();
+                                        }
+                                        Err(err) => {
+                                            eprintln!("[Dokument-Fehler] Konnte Backup für '{id}' nicht wiederherstellen: {err}");
+                                            ui_state.set_export_message(format!("Wiederherstellung fehlgeschlagen: {err}"));
+                                        }
+                                    }
+                                }
+                                UiAction::OpenNotebookFolder(id) => {
+                                    let target_dir = storage_base_dir.join(&id);
+                                    ui_state.set_export_message(format!("Ordner: {}", target_dir.display()));
+                                    window.request_redraw();
+                                }
                                 UiAction::CheckForUpdates => {
                                     updater.check_for_updates();
                                     window.request_redraw();
@@ -2118,6 +2271,51 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                                     ui_state.set_export_message("Server-Einstellungen gespeichert");
                                     window.request_redraw();
                                 }
+                                UiAction::UnlockCorruptedPage(page_id) => {
+                                    notebook.load_warnings.remove(&page_id);
+                                    if let Some(page) = notebook.pages.iter_mut().find(|p| p.id == page_id) {
+                                        page.unlock_after_load_error();
+                                    }
+                                    autosave.mark_dirty(&notebook, &mut manifest);
+                                    window.request_redraw();
+                                }
+                                UiAction::RetryShutdown => {
+                                    println!("[Shutdown] Wiederhole Speichern vor Beenden...");
+                                    match autosave.shutdown() {
+                                        Ok(()) => {
+                                            ui_state.shutdown_error = None;
+                                            target.exit();
+                                        }
+                                        Err(err) => {
+                                            ui_state.shutdown_error = Some(err);
+                                            window.request_redraw();
+                                        }
+                                    }
+                                }
+                                UiAction::ExportRecoveryAndExit => {
+                                    println!("[Shutdown] Starte Notfall-Export aller ungespeicherten Daten...");
+                                    match autosave.export_recovery(Some(&notebook)) {
+                                        Ok(paths) => {
+                                            eprintln!(
+                                                "[Recovery] Notfall-Export erfolgreich geschrieben ({} Dateien): {:?}",
+                                                paths.len(),
+                                                paths
+                                            );
+                                            target.exit();
+                                        }
+                                        Err(err) => {
+                                            eprintln!("[Recovery-Fehler] Konnte Notfall-Export nicht schreiben: {err}");
+                                            if let Some(ref mut se) = ui_state.shutdown_error {
+                                                se.messages.push(format!("Notfall-Export fehlgeschlagen: {err}"));
+                                            }
+                                            window.request_redraw();
+                                        }
+                                    }
+                                }
+                                UiAction::ForceExit => {
+                                    println!("[Shutdown] Beenden erzwungen trotz ungespeicherter Änderungen.");
+                                    target.exit();
+                                }
                             }
                         }
 

src/spline.rs

@@ -105,6 +105,18 @@ impl Default for SplineConfig {
     }
 }
 
+impl SplineConfig {
+    /// Erzeugt eine Spline-Konfiguration aus der Strichbreite in internen Einheiten (10 Einheiten = 1 mm).
+    pub fn from_width_units(width_units: f32) -> Self {
+        let base_radius = (width_units / 2.0).max(0.25);
+        Self {
+            min_radius: (base_radius * 0.5).max(0.15),
+            max_radius: (base_radius * 1.5).max(0.35),
+            samples_per_segment: 16,
+        }
+    }
+}
+
 /// Berechnet den druckabhängigen Radius r(p) = min_r + p * (max_r - min_r).
 pub fn calculate_radius(pressure: f32, min_radius: f32, max_radius: f32) -> f32 {
     let p = pressure.clamp(0.0, 1.0);
@@ -653,7 +665,10 @@ pub fn finalize_stroke_with_config(
         .map(|v| InkVertex::new(v.position[0], v.position[1], color))
         .collect();
 
-    Stroke::new(stroke_id, decimated, ink_vertices, color)
+    let mut stroke = Stroke::new(stroke_id, decimated, ink_vertices, color);
+    stroke.width = config.min_radius + config.max_radius;
+    stroke.finalized = true;
+    stroke
 }
 
 #[cfg(test)]

src/ui.rs

@@ -113,6 +113,9 @@ pub enum UiAction {
         new_title: String,
     },
     DeleteNotebook(String),
+    UndoDeleteNotebook,
+    RestoreNotebookBackup(String),
+    OpenNotebookFolder(String),
     RefreshNotebooks,
     // Gitea Release & Updater
     CheckForUpdates,
@@ -123,6 +126,12 @@ pub enum UiAction {
         server_url: String,
         auth_token: Option<String>,
     },
+    // Datenintegrität / Quarantäne
+    UnlockCorruptedPage(u64),
+    // Beenden-Sicherheit bei Fehlschlag
+    RetryShutdown,
+    ExportRecoveryAndExit,
+    ForceExit,
 }
 
 /// Zustand der grafischen Benutzeroberfläche.
@@ -162,6 +171,10 @@ pub struct UiState {
     pub update_modal_rect: Option<egui::Rect>,
     /// Steuert, ob Touch-Eingaben mit einem Finger zeichnen oder das Dokument verschieben (Default: false = reine Gesten-Navigation & Zoom)
     pub touch_draw_enabled: bool,
+    /// Zuletzt gelöschtes Notizbuch für Rückgängig während der Sitzung (Papierkorb-Pfad, Titel)
+    pub last_deleted_notebook: Option<(std::path::PathBuf, String)>,
+    /// Fehler beim Flushen vor dem Beenden
+    pub shutdown_error: Option<crate::autosave::AutosaveError>,
 }
 
 impl Default for UiState {
@@ -193,6 +206,8 @@ impl Default for UiState {
             show_updater_config: false,
             update_modal_rect: None,
             touch_draw_enabled: false,
+            last_deleted_notebook: None,
+            shutdown_error: None,
         }
     }
 }
@@ -1546,11 +1561,17 @@ pub fn render_ui(
                                                             .size(13.0)
                                                             .color(egui::Color32::WHITE),
                                                     );
-                                                    if is_current {
+                                                    if summary.status == crate::storage::NotebookStatus::Damaged {
+                                                        ui.colored_label(egui::Color32::from_rgb(255, 100, 100), "⚠️ Beschädigt");
+                                                    } else if is_current {
                                                         ui.colored_label(egui::Color32::from_rgb(46, 204, 113), "● Aktiv");
                                                     }
                                                 });
-                                                let subtext = format!("{} Seite(n)", summary.page_count);
+                                                let subtext = if let Some(ref err) = summary.error {
+                                                    format!("Fehler: {err}")
+                                                } else {
+                                                    format!("{} Seite(n)", summary.page_count)
+                                                };
                                                 ui.label(
                                                     egui::RichText::new(subtext)
                                                         .size(11.0)
@@ -1559,27 +1580,47 @@ pub fn render_ui(
                                             });
 
                                             ui.with_layout(egui::Layout::right_to_left(egui::Align::Center), |ui| {
-                                                if state.available_notebooks.len() > 1
-                                                    && ui
-                                                        .button(egui::RichText::new("🗑").size(11.0).color(egui::Color32::from_rgb(255, 120, 120)))
-                                                        .on_hover_text("Notizbuch unwiderruflich löschen")
+                                                if summary.status == crate::storage::NotebookStatus::Damaged {
+                                                    if ui
+                                                        .button(egui::RichText::new("🔄 Backup").size(11.0).color(egui::Color32::from_rgb(100, 200, 255)))
+                                                        .on_hover_text("Aus manifest.json.bak wiederherstellen")
                                                         .clicked()
-                                                {
-                                                    actions.push(UiAction::DeleteNotebook(summary.id.clone()));
-                                                }
+                                                    {
+                                                        actions.push(UiAction::RestoreNotebookBackup(summary.id.clone()));
+                                                    }
+                                                    if ui
+                                                        .button(egui::RichText::new("📁 Ordner").size(11.0))
+                                                        .on_hover_text("Pfad in Statusleiste anzeigen")
+                                                        .clicked()
+                                                    {
+                                                        actions.push(UiAction::OpenNotebookFolder(summary.id.clone()));
+                                                    }
+                                                } else {
+                                                    if state.available_notebooks.len() > 1
+                                                        && ui
+                                                            .button(egui::RichText::new("🗑").size(11.0).color(egui::Color32::from_rgb(255, 120, 120)))
+                                                            .on_hover_text("Notizbuch in Papierkorb verschieben")
+                                                            .clicked()
+                                                    {
+                                                        actions.push(UiAction::DeleteNotebook(summary.id.clone()));
+                                                    }
 
-                                                if ui.button(egui::RichText::new("✏").size(11.0))
-                                                    .on_hover_text("Titel umbenennen")
-                                                    .clicked()
-                                                {
-                                                    state.renaming_notebook_id = Some(summary.id.clone());
-                                                    state.renaming_title_input = summary.title.clone();
+                                                    if ui.button(egui::RichText::new("✏").size(11.0))
+                                                        .on_hover_text("Titel umbenennen")
+                                                        .clicked()
+                                                    {
+                                                        state.renaming_notebook_id = Some(summary.id.clone());
+                                                        state.renaming_title_input = summary.title.clone();
+                                                    }
                                                 }
                                             });
                                         });
                                     });
 
-                                if frame_resp.response.interact(egui::Sense::click()).clicked() && !is_current {
+                                if summary.status != crate::storage::NotebookStatus::Damaged
+                                    && frame_resp.response.interact(egui::Sense::click()).clicked()
+                                    && !is_current
+                                {
                                     actions.push(UiAction::OpenNotebook(summary.id.clone()));
                                     state.is_document_menu_open = false;
                                 }
@@ -1589,6 +1630,23 @@ pub fn render_ui(
                     }
                 });
 
+                if let Some((_, ref title)) = state.last_deleted_notebook {
+                    ui.add_space(4.0);
+                    ui.horizontal(|ui| {
+                        ui.label(
+                            egui::RichText::new(format!("'{title}' gelöscht"))
+                                .size(11.0)
+                                .color(egui::Color32::from_rgb(255, 180, 100)),
+                        );
+                        if ui
+                            .button(egui::RichText::new("↩ Rückgängig").size(11.0).color(egui::Color32::from_rgb(100, 200, 255)))
+                            .clicked()
+                        {
+                            actions.push(UiAction::UndoDeleteNotebook);
+                        }
+                    });
+                }
+
                 ui.add_space(8.0);
                 ui.separator();
                 ui.add_space(4.0);
@@ -1932,6 +1990,183 @@ pub fn render_ui(
         }
     }
 
+    // 5. Nicht-wegklickbare Warnung bei Ladefehlern / Quarantäne (Block 1)
+    if let Some(warning) = notebook.load_warnings.get(&notebook.current_page().id) {
+        egui::Window::new("⚠️ Datenintegritäts-Warnung")
+            .collapsible(false)
+            .resizable(false)
+            .anchor(egui::Align2::CENTER_CENTER, egui::vec2(0.0, 0.0))
+            .frame(
+                egui::Frame::none()
+                    .fill(egui::Color32::from_rgba_premultiplied(35, 20, 20, 245))
+                    .rounding(egui::Rounding::same(12.0))
+                    .stroke(egui::Stroke::new(
+                        1.5_f32,
+                        egui::Color32::from_rgb(235, 87, 87),
+                    ))
+                    .inner_margin(egui::Margin::symmetric(24.0, 20.0))
+                    .shadow(egui::epaint::Shadow {
+                        offset: egui::vec2(0.0, 8.0),
+                        blur: 24.0,
+                        spread: 0.0,
+                        color: egui::Color32::from_black_alpha(180),
+                    }),
+            )
+            .show(ctx, |ui| {
+                ui.set_width(420.0);
+                ui.horizontal(|ui| {
+                    ui.colored_label(egui::Color32::from_rgb(255, 80, 80), "⚠️");
+                    ui.label(
+                        egui::RichText::new(format!(
+                            "Seite {} konnte nicht fehlerfrei geladen werden!",
+                            warning.page_id
+                        ))
+                        .strong()
+                        .size(15.0)
+                        .color(egui::Color32::WHITE),
+                    );
+                });
+                ui.add_space(8.0);
+                ui.label(
+                    egui::RichText::new(format!("Fehlermeldung: {}", warning.message))
+                        .size(12.0)
+                        .color(egui::Color32::from_gray(200)),
+                );
+                ui.add_space(8.0);
+                if let Some(ref q_path) = warning.quarantine_path {
+                    ui.label(
+                        egui::RichText::new("Die beschädigte Originaldatei wurde in Quarantäne gesichert:")
+                            .size(12.0)
+                            .color(egui::Color32::from_gray(220)),
+                    );
+                    ui.add_space(4.0);
+                    ui.monospace(
+                        egui::RichText::new(q_path.display().to_string())
+                            .size(11.0)
+                            .color(egui::Color32::from_rgb(255, 215, 0)),
+                    );
+                    ui.add_space(10.0);
+                    ui.label(
+                        egui::RichText::new(
+                            "Um Datenverlust zu verhindern, ist diese Seite schreibgeschützt.\n\
+                             Wenn Sie diese Seite bearbeiten möchten, können Sie den Schreibschutz aufheben.",
+                        )
+                        .size(11.5)
+                        .color(egui::Color32::from_gray(180)),
+                    );
+                    ui.add_space(12.0);
+                    if ui
+                        .button(
+                            egui::RichText::new("Als leere Seite bearbeiten (Schreibschutz aufheben)")
+                                .color(egui::Color32::WHITE)
+                                .size(12.5),
+                        )
+                        .clicked()
+                    {
+                        actions.push(UiAction::UnlockCorruptedPage(warning.page_id));
+                    }
+                } else {
+                    ui.label(
+                        egui::RichText::new(
+                            "Zugriffsfehler (I/O). Die Datei existiert, kann aber nicht gelesen werden.\n\
+                             Die Seite bleibt schreibgeschützt, um ein Überschreiben zu verhindern.",
+                        )
+                        .size(12.0)
+                        .color(egui::Color32::from_gray(200)),
+                    );
+                }
+            });
+    }
+
+    // Notfall-/Sicherheits-Dialog bei Fehlschlag des Speicherns vor dem Beenden
+    if let Some(err) = &state.shutdown_error {
+        let mut dismiss = false;
+        egui::Window::new("⚠️ Ungespeicherte Änderungen")
+            .collapsible(false)
+            .resizable(false)
+            .anchor(egui::Align2::CENTER_CENTER, egui::vec2(0.0, 0.0))
+            .frame(
+                egui::Frame::none()
+                    .fill(egui::Color32::from_rgba_premultiplied(35, 20, 20, 250))
+                    .rounding(egui::Rounding::same(12.0))
+                    .stroke(egui::Stroke::new(
+                        1.5_f32,
+                        egui::Color32::from_rgb(235, 87, 87),
+                    ))
+                    .inner_margin(egui::Margin::symmetric(24.0, 20.0))
+                    .shadow(egui::epaint::Shadow {
+                        offset: egui::vec2(0.0, 8.0),
+                        blur: 24.0,
+                        spread: 0.0,
+                        color: egui::Color32::from_black_alpha(200),
+                    }),
+            )
+            .show(ctx, |ui| {
+                ui.set_width(460.0);
+                ui.horizontal(|ui| {
+                    ui.colored_label(egui::Color32::from_rgb(255, 80, 80), "⚠️");
+                    ui.label(
+                        egui::RichText::new("Fehler beim Beenden")
+                            .color(egui::Color32::from_rgb(255, 100, 100))
+                            .size(16.0)
+                            .strong(),
+                    );
+                });
+                ui.add_space(8.0);
+                ui.label(
+                    egui::RichText::new(
+                        "Ungespeicherte Änderungen konnten nicht gesichert werden:",
+                    )
+                    .size(13.0)
+                    .color(egui::Color32::WHITE),
+                );
+                ui.add_space(6.0);
+                egui::Frame::none()
+                    .fill(egui::Color32::from_black_alpha(100))
+                    .rounding(egui::Rounding::same(6.0))
+                    .inner_margin(egui::Margin::same(8.0))
+                    .show(ui, |ui| {
+                        for msg in &err.messages {
+                            ui.label(
+                                egui::RichText::new(msg)
+                                    .size(11.5)
+                                    .color(egui::Color32::from_rgb(255, 180, 180)),
+                            );
+                        }
+                    });
+                ui.add_space(8.0);
+                ui.label(
+                    egui::RichText::new("Trotzdem beenden?")
+                        .size(13.0)
+                        .color(egui::Color32::WHITE),
+                );
+                ui.add_space(12.0);
+                ui.horizontal_wrapped(|ui| {
+                    if ui.button("Abbrechen").clicked() {
+                        dismiss = true;
+                    }
+                    if ui.button("Wiederholen").clicked() {
+                        actions.push(UiAction::RetryShutdown);
+                    }
+                    if ui.button("Notfall-Export").clicked() {
+                        actions.push(UiAction::ExportRecoveryAndExit);
+                    }
+                    if ui
+                        .button(
+                            egui::RichText::new("Trotzdem beenden")
+                                .color(egui::Color32::from_rgb(255, 100, 100)),
+                        )
+                        .clicked()
+                    {
+                        actions.push(UiAction::ForceExit);
+                    }
+                });
+            });
+        if dismiss {
+            state.shutdown_error = None;
+        }
+    }
+
     actions
 }
 
@@ -2058,12 +2293,16 @@ mod tests {
                 title: "Mathematik I".to_string(),
                 page_count: 3,
                 modified_at: 100,
+                status: crate::storage::NotebookStatus::Normal,
+                error: None,
             },
             NotebookSummary {
                 id: "nb-2".to_string(),
                 title: "Physik II".to_string(),
                 page_count: 5,
                 modified_at: 200,
+                status: crate::storage::NotebookStatus::Normal,
+                error: None,
             },
         ];
         state.current_notebook_id = "nb-1".to_string();