feat: Windows build and Android groundwork (Issues #48, #42)

Shared groundwork:
- paths.rs: folders for data, settings and downloads per system (Linux XDG
  unchanged, Windows %APPDATA%/%LOCALAPPDATA%, Android app folder)
- Linux-only parts behind cfg: Wayland on-screen keyboard (osk/wayland.rs),
  display backend and app id, the vendored winit touch extensions
- run_with(event_loop) so that other entry points can start the app

Windows (#48):
- cross-compiled with MinGW into a portable ink-notes_<version>_x86_64.exe
  (system DLLs only), no console window in release builds
- file picker: user folders and drives; held notebook locks are detected
  (ERROR_LOCK_VIOLATION)
- updater: replaces the running .exe via rename, active at the next start
- octotablet panicking without the Tablet PC components no longer crashes
  the app
- release: .exe built in CI and part of the signed checksums
- all library tests pass under wine

Android (#42):
- android_main entry point, winit with android-native-activity,
  android_logger; octotablet and arboard left out there
- cargo check and the cdylib build for aarch64-linux-android pass; the window
  surface does not follow the activity lifecycle yet

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

scripts/build-release.sh

@@ -1,7 +1,7 @@
 #!/usr/bin/env bash
 # ==============================================================================
 # Haupt-Release-Build-Skript für ink-notes (Zorin OS 18 / Linux)
-# Erstellt .deb, .AppImage, SHA256-Prüfsummen und deren Minisign-Signatur in target/
+# Erstellt .deb, .AppImage, Windows-.exe, SHA256-Prüfsummen und deren Minisign-Signatur in target/
 # ==============================================================================
 set -euo pipefail
 
@@ -13,6 +13,7 @@ cd "${ROOT_DIR}"
 VERSION=$(grep -m1 '^version = ' Cargo.toml | cut -d '"' -f2)
 DEB_NAME="ink-notes_${VERSION}_amd64.deb"
 APPIMAGE_NAME="ink-notes_${VERSION}_x86_64.AppImage"
+EXE_NAME="ink-notes_${VERSION}_x86_64.exe"
 CHECKSUM_FILE="SHA256SUMS.txt"
 
 echo "======================================================================"
@@ -25,12 +26,15 @@ echo "======================================================================"
 # 2. AppImage bauen (.AppImage)
 "${SCRIPT_DIR}/package-appimage.sh"
 
-# 3. Checksums berechnen
+# 3. Portable Windows program (.exe)
+"${SCRIPT_DIR}/package-windows.sh"
+
+# 4. Checksums berechnen
 echo "=== Berechne SHA256-Prüfsummen in target/${CHECKSUM_FILE} ==="
 cd "${ROOT_DIR}/target"
-sha256sum "${DEB_NAME}" "${APPIMAGE_NAME}" > "${CHECKSUM_FILE}"
+sha256sum "${DEB_NAME}" "${APPIMAGE_NAME}" "${EXE_NAME}" > "${CHECKSUM_FILE}"
 
-# 4. Prüfsummen signieren (Pflicht für In-App-Updates)
+# 5. Prüfsummen signieren (Pflicht für In-App-Updates)
 # Signiert wird mit rsign2 (minisign-kompatibles Format): Der Schlüssel wurde mit
 # `rsign generate -W` erzeugt; das minisign-CLI kann ihn ohne Terminal nicht laden.
 SIGNATURE_FILE="${CHECKSUM_FILE}.minisig"
@@ -73,7 +77,7 @@ fi
 echo "======================================================================"
 echo "Release-Artefakte für v${VERSION} erfolgreich erstellt:"
 echo "======================================================================"
-ls -lh "${DEB_NAME}" "${APPIMAGE_NAME}" "${CHECKSUM_FILE}"
+ls -lh "${DEB_NAME}" "${APPIMAGE_NAME}" "${EXE_NAME}" "${CHECKSUM_FILE}"
 if [ -f "${SIGNATURE_FILE}" ]; then ls -lh "${SIGNATURE_FILE}"; fi
 echo ""
 echo "Inhalt von target/${CHECKSUM_FILE}:"

scripts/package-windows.sh

@@ -0,0 +1,28 @@
+#!/usr/bin/env bash
+# ==============================================================================
+# Builds the portable Windows program target/ink-notes_<version>_x86_64.exe (Issue #48)
+# by cross-compiling on Linux. Needs the MinGW-w64 compiler
+# (Debian/Ubuntu: gcc-mingw-w64-x86-64) for the C parts of the dependencies.
+# ==============================================================================
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+ROOT_DIR="$(cd "${SCRIPT_DIR}/.." && pwd)"
+cd "${ROOT_DIR}"
+
+TARGET="x86_64-pc-windows-gnu"
+VERSION=$(grep -m1 '^version = ' Cargo.toml | cut -d '"' -f2)
+EXE_NAME="ink-notes_${VERSION}_x86_64.exe"
+
+if ! command -v x86_64-w64-mingw32-gcc >/dev/null 2>&1; then
+    echo "FEHLER: x86_64-w64-mingw32-gcc nicht gefunden (Paket gcc-mingw-w64-x86-64)."
+    exit 1
+fi
+if command -v rustup >/dev/null 2>&1; then
+    rustup target add "${TARGET}"
+fi
+
+echo "=== Baue ${EXE_NAME} ==="
+cargo build --release --target "${TARGET}"
+cp "${CARGO_TARGET_DIR:-target}/${TARGET}/release/ink-notes.exe" "target/${EXE_NAME}"
+ls -lh "target/${EXE_NAME}"

scripts/publish-gitea-release.sh

@@ -1,7 +1,7 @@
 #!/usr/bin/env bash
 # ==============================================================================
 # Veröffentlicht ein Release auf dem Gitea-Server (gitea.pansi.eu)
-# Lädt .deb, .AppImage, SHA256SUMS.txt und SHA256SUMS.txt.minisig idempotent als Release-Assets hoch.
+# Lädt .deb, .AppImage, .exe, SHA256SUMS.txt und SHA256SUMS.txt.minisig idempotent als Release-Assets hoch.
 # ==============================================================================
 set -euo pipefail
 
@@ -32,6 +32,7 @@ RELEASE_TITLE="ink-notes ${TAG_NAME}"
 
 DEB_FILE="${ROOT_DIR}/target/ink-notes_${VERSION}_amd64.deb"
 APPIMAGE_FILE="${ROOT_DIR}/target/ink-notes_${VERSION}_x86_64.AppImage"
+EXE_FILE="${ROOT_DIR}/target/ink-notes_${VERSION}_x86_64.exe"
 CHECKSUMS_FILE="${ROOT_DIR}/target/SHA256SUMS.txt"
 SIGNATURE_FILE="${CHECKSUMS_FILE}.minisig"
 TEMPLATE_FILE="${ROOT_DIR}/packaging/release-notes.md.tmpl"
@@ -42,7 +43,7 @@ if [ ! -f "${TEMPLATE_FILE}" ]; then
 fi
 
 # Sicherstellen, dass die Artefakte existieren
-if [ ! -f "${DEB_FILE}" ] || [ ! -f "${APPIMAGE_FILE}" ] || [ ! -f "${CHECKSUMS_FILE}" ]; then
+if [ ! -f "${DEB_FILE}" ] || [ ! -f "${APPIMAGE_FILE}" ] || [ ! -f "${EXE_FILE}" ] || [ ! -f "${CHECKSUMS_FILE}" ]; then
     echo "Artefakte nicht vollständig gefunden. Führe build-release.sh aus..."
     "${SCRIPT_DIR}/build-release.sh"
 fi
@@ -236,6 +237,7 @@ except Exception:
 
 upload_asset "${DEB_FILE}"
 upload_asset "${APPIMAGE_FILE}"
+upload_asset "${EXE_FILE}"
 upload_asset "${CHECKSUMS_FILE}"
 upload_asset "${SIGNATURE_FILE}"