feat: integrate Tauri v2 with Android widget and voice assistant

- Add Tauri v2 shell (Cargo, tauri.conf.json, capabilities, plugins)
- Migrate all fetch() calls to apiFetch() for Tauri-aware HTTP
- Migrate WebSocket endpoints to resolveEndpoints() for dynamic URLs
- Add ServerConfigDialog for remote server URL configuration
- Add tauri.ts lib with isTauri detection, apiFetch wrapper, plugin helpers
- Add server-config Pinia store with persistence via plugin-store
- Conditional PWA (disabled in Tauri builds)
- Android: home screen transcript widget (last 5 messages, 30s refresh)
- Android: voice command / share activity (SpeechRecognizer + WebSocket)
- Android: signed release APK with auto-copy to installers/
- Remove stale frontend/src-tauri directory

package.json

@@ -7,7 +7,12 @@
     "start": "bun run kill-ports && concurrently -n api,terminal,frontend -c blue,yellow,green \"cd server && bun --watch run index.ts\" \"cd server && bun run terminal.ts\" \"cd frontend && bun run dev --host\"",
     "start:api": "cd server && bun --watch run index.ts",
     "start:terminal": "cd server && bun run terminal.ts",
-    "start:frontend": "cd frontend && bun run dev --host"
+    "start:frontend": "cd frontend && bun run dev --host",
+    "tauri": "npx --prefix frontend tauri",
+    "tauri:dev": "npx --prefix frontend tauri dev",
+    "tauri:build": "npx --prefix frontend tauri build",
+    "tauri:android:init": "npx --prefix frontend tauri android init",
+    "tauri:android:build": "npx --prefix frontend tauri android build"
   },
   "devDependencies": {
     "concurrently": "^9.2.1"