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

frontend/src/lib/tauri.ts

@@ -0,0 +1,85 @@
+/**
+ * Tauri detection and fetch wrapper for Agent UI.
+ * In Tauri mode, relative /api/... paths are resolved against the configured server URL.
+ * In web mode, this is a transparent pass-through to native fetch.
+ */
+
+// Detect if running inside a Tauri webview
+export const isTauri = '__TAURI_INTERNALS__' in window
+
+// Detect mobile Tauri (Android/iOS)
+export function isMobileTauri(): boolean {
+  if (!isTauri) return false
+  const ua = navigator.userAgent.toLowerCase()
+  return /android|iphone|ipad|ipod/.test(ua)
+}
+
+// Server URL storage (in-memory, loaded from Tauri store on init)
+let _serverUrl = ''
+
+export function getServerUrl(): string {
+  return _serverUrl
+}
+
+export function setServerUrl(url: string) {
+  // Normalize: remove trailing slash
+  _serverUrl = url.replace(/\/+$/, '')
+}
+
+/**
+ * Resolve a path to a full URL.
+ * - In web mode: returns the path as-is (relative URLs work with Vite proxy / reverse proxy)
+ * - In Tauri mode: prepends the configured server URL
+ */
+export function resolveUrl(path: string): string {
+  if (!isTauri) return path
+  if (!_serverUrl) {
+    console.warn('[Tauri] No server URL configured, using path as-is:', path)
+    return path
+  }
+  // If already absolute, return as-is
+  if (path.startsWith('http://') || path.startsWith('https://')) return path
+  return `${_serverUrl}${path}`
+}
+
+/**
+ * Fetch wrapper that resolves relative API paths in Tauri mode.
+ * In Tauri, uses @tauri-apps/plugin-http for proper CORS-free requests.
+ * In web, delegates to native fetch.
+ */
+export async function apiFetch(input: string | URL | Request, init?: RequestInit): Promise<Response> {
+  if (!isTauri) {
+    return fetch(input, init)
+  }
+
+  // Resolve URL
+  const url = typeof input === 'string' ? resolveUrl(input) : input
+
+  // Use Tauri HTTP plugin for cross-origin requests
+  try {
+    const { fetch: tauriFetch } = await import('@tauri-apps/plugin-http')
+    return tauriFetch(url, init)
+  } catch (e) {
+    // Fallback to native fetch if plugin fails
+    console.warn('[Tauri] HTTP plugin failed, falling back to fetch:', e)
+    return fetch(url, init)
+  }
+}
+
+// Dynamic plugin imports (only used behind isTauri checks)
+export async function getTauriStore() {
+  const { LazyStore } = await import('@tauri-apps/plugin-store')
+  return new LazyStore('settings.json')
+}
+
+export async function getTauriNotification() {
+  return import('@tauri-apps/plugin-notification')
+}
+
+export async function getTauriClipboard() {
+  return import('@tauri-apps/plugin-clipboard-manager')
+}
+
+export async function getTauriDialog() {
+  return import('@tauri-apps/plugin-dialog')
+}