fix: recurring event display and AI query improvements

- Use occurrenceStart instead of startTime in getEventsInRange so
  recurring events show their actual occurrence date to the AI
- Add lazy CalDAV sync in ChatService (syncOnce before first DB access)
- Add CaldavService.sync() with internal config check (silent no-op)
- Show German recurrence description (e.g. "Jede Woche") instead of
  generic "Wiederkehrend" in EventCardBase via formatRecurrenceRule()
- Move RepeatType and REPEAT_TYPE_LABELS from editEvent to shared
- Separate calendar overlay useFocusEffect from event loading

apps/server/src/app.ts

@@ -62,12 +62,13 @@ const aiProvider = new GPTAdapter();
 // Initialize services
 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 caldavService = new CaldavService(caldavRepo, eventService);
 
 // Initialize controllers
 const authController = new AuthController(authService);