feat: add in-app notifications system with bell icon, polling, and notifications page

js/app.js

@@ -1,6 +1,7 @@
 import { i18n } from './i18n.js'
 import { auth } from './services/auth.js'
 import { favoritesService } from './services/favorites.js'
+import { notificationsService } from './services/notifications.js'
 import { setupGlobalErrorHandler } from './components/error-boundary.js'
 
 async function initApp() {
@@ -17,6 +18,7 @@ async function initApp() {
     // Restore auth session before loading components
     await auth.tryRestoreSession()
     favoritesService.init()
+    notificationsService.init()
 
     await import('./components/app-shell.js')