- Updated BookingRequest validator to use NOTE_MAX_LENGTH constant
- Replaced hardcoded 144 with constant for consistency
- Error message now includes the actual max length value
- Create Availability model with date, start_time, end_time
- Add availability schemas with 15-minute boundary validation
- Add admin endpoints:
- GET /api/admin/availability - query by date range
- PUT /api/admin/availability - set slots for a date
- POST /api/admin/availability/copy - copy to multiple days
- Add 26 tests covering permissions, CRUD, and validation