- Added get_job_pool() for lazy pool initialization
- Added close_job_pool() for graceful shutdown
- Hooked pool shutdown into FastAPI lifespan
- Reuses connections instead of creating new ones per enqueue
- Add ruff as dev dependency
- Configure ruff in pyproject.toml with strict 88-char line limit
- Ignore B008 (FastAPI Depends pattern is standard)
- Allow longer lines in tests for readability
- Fix all lint issues in source files
- Add Makefile targets: lint-backend, format-backend, fix-backend
- 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
