Fix missing SYNC_MODE_CALDAV import in sensor.py

custom_components/room_cal_ha/sensor.py

@@ -19,6 +19,7 @@ from .const import (
   STORE_CURRENT,
   STORE_NEXT,
   SYNC_MODE_API,
+  SYNC_MODE_CALDAV,
   SYNC_MODE_MANUAL,
 )
 from .coordinator import CoordinatorData, RoomCalCoordinator