feat(events): recurring expansion, CalDAV pull sync, past search, reminders

- RRULE expansion: list_events now expands recurring events into
  individual occurrences within the query window using python-dateutil
- CalDAV pull sync: new caldav_sync.py + POST /api/events/sync route;
  imports remote events into the internal store by caldav_uid
- Past event search: search_events accepts include_past=true to search
  historical events; exposed in the LLM tool definition
- Internal reminders: migration 0037 adds reminder_minutes +
  reminder_sent_at columns; event_scheduler.py checks every 5 min and
  fires push notifications; CalDAV sync job runs hourly
- reminder_minutes now stored and returned in create/update routes + tools

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/fabledassistant/app.py

@@ -317,6 +317,10 @@ def create_app() -> Quart:
         from fabledassistant.services.briefing_scheduler import start_briefing_scheduler
         await start_briefing_scheduler(asyncio.get_running_loop())
 
+        # Start event scheduler (reminders + CalDAV pull sync)
+        from fabledassistant.services.event_scheduler import start_event_scheduler
+        start_event_scheduler(asyncio.get_running_loop())
+
         # Voice model loading (enabled via Admin → Config in the UI, or VOICE_ENABLED env var)
         from fabledassistant.services.stt import load_stt_model
         from fabledassistant.services.tts import load_tts_model
@@ -327,6 +331,8 @@ def create_app() -> Quart:
     async def shutdown():
         from fabledassistant.services.briefing_scheduler import stop_briefing_scheduler
         stop_briefing_scheduler()
+        from fabledassistant.services.event_scheduler import stop_event_scheduler
+        stop_event_scheduler()
 
     @app.route("/")
     async def serve_index():