Migrate to Electron and implement native PDF export

Major changes:
- Migrate from Tauri to Electron as primary desktop runtime
- Implement native print dialog for PDF export via Electron webview
- Add desktop runtime abstraction layer (supports both Electron and Tauri)
- Implement task list rendering in preview mode
- Add favorite notes sorting to display starred notes at top
- Add attachment upload functionality with file picker
- Improve sync reliability and Unicode filename support
- Add category color sync across devices via WebDAV
- Update documentation for Electron workflow

Technical improvements:
- Add Electron main process and preload bridge
- Create desktop service layer for runtime-agnostic operations
- Implement runtimeFetch for proxying network requests through Electron
- Add PrintView component for native print rendering
- Extract print/PDF utilities to shared module
- Update build configuration for Electron integration

package.json

@@ -2,10 +2,18 @@
   "name": "nextcloud-notes-tauri",
   "private": true,
   "version": "0.2.2",
+  "description": "Desktop client for Nextcloud Notes built with Electron, React, and TypeScript.",
   "type": "module",
+  "main": "electron/main.cjs",
   "scripts": {
     "dev": "vite",
+    "dev:renderer": "vite",
+    "dev:electron": "wait-on tcp:1420 && cross-env ELECTRON_RENDERER_URL=http://localhost:1420 electron .",
+    "dev:desktop": "concurrently -k \"npm:dev:renderer\" \"npm:dev:electron\"",
     "build": "tsc && vite build",
+    "desktop": "electron .",
+    "dist:dir": "npm run build && electron-builder --dir",
+    "dist:mac": "npm run build && electron-builder --mac dmg zip",
     "preview": "vite preview",
     "tauri": "tauri"
   },
@@ -34,9 +42,50 @@
     "@types/turndown": "^5.0.6",
     "@vitejs/plugin-react": "^4.6.0",
     "autoprefixer": "^10.4.27",
+    "concurrently": "^9.2.1",
+    "cross-env": "^10.1.0",
+    "electron": "^37.3.1",
+    "electron-builder": "^26.8.1",
     "postcss": "^8.5.8",
     "tailwindcss": "^3.4.19",
     "typescript": "~5.8.3",
-    "vite": "^7.0.4"
+    "vite": "^7.0.4",
+    "wait-on": "^8.0.5"
+  },
+  "build": {
+    "appId": "cz.davidrelich.nextcloud-notes-desktop",
+    "productName": "Nextcloud Notes Desktop",
+    "directories": {
+      "output": "release"
+    },
+    "files": [
+      "dist/**/*",
+      "electron/**/*",
+      "package.json"
+    ],
+    "asar": true,
+    "npmRebuild": false,
+    "mac": {
+      "category": "public.app-category.productivity",
+      "icon": "src-tauri/icons/icon.icns",
+      "target": [
+        "dmg",
+        "zip"
+      ]
+    },
+    "win": {
+      "icon": "src-tauri/icons/icon.ico",
+      "target": [
+        "nsis",
+        "zip"
+      ]
+    },
+    "linux": {
+      "icon": "src-tauri/icons/icon.png",
+      "target": [
+        "AppImage",
+        "deb"
+      ]
+    }
   }
 }