Fix Resos sync interrupted by health check restart

Yield to event loop after each booking DB commit so FastAPI can
respond to Docker health checks during long syncs.

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

backend/jobs/resos_bookings_sync.py

@@ -3,6 +3,7 @@ Resos Bookings Data Sync Job
 Syncs restaurant bookings to resos_bookings_data table
 Pattern: Replicates newbook bookings sync but adapted for Resos covers/stats
 """
+import asyncio
 import json
 import logging
 from datetime import date, datetime, timedelta
@@ -328,6 +329,7 @@ async def sync_resos_bookings_data(
                     records_created += 1
 
                 db.commit()
+                await asyncio.sleep(0)  # yield to event loop so health checks pass
 
             # Update sync log
             db.execute(