- Add create() and create_multiple() methods to AvailabilityRepository
- Update AvailabilityService to use repository methods instead of direct db operations
- Create AvailabilityService with get_availability_for_range(), set_availability_for_date(), and copy_availability()
- Move slot validation logic to service
- Update routes/availability.py to use AvailabilityService
- Remove all direct database queries from routes