refactor: reduce CalDAV sync to login and manual sync button only

- Remove auto-login sync in AuthGuard
- Remove 10s interval sync and syncAndReload in calendar tab
- Remove lazy syncOnce pattern in ChatService AI callbacks
- Remove CaldavService dependency from ChatService constructor

apps/server/src/app.ts

@@ -63,12 +63,7 @@ const aiProvider = new GPTAdapter();
 const authService = new AuthService(userRepo);
 const eventService = new EventService(eventRepo);
 const caldavService = new CaldavService(caldavRepo, eventService);
-const chatService = new ChatService(
-  chatRepo,
-  eventService,
-  aiProvider,
-  caldavService,
-);
+const chatService = new ChatService(chatRepo, eventService, aiProvider);
 
 // Initialize controllers
 const authController = new AuthController(authService);