Issue #5: Date validation logic was duplicated across availability
and booking routes.
Changes:
- Add date_validation.py with shared utilities:
- get_bookable_date_range: returns (min_date, max_date) tuple
- validate_date_in_range: validates date with contextual errors
- Update routes/availability.py to use shared utilities
- Update routes/booking.py to use shared utilities
- Remove redundant _get_date_range_bounds and _get_bookable_date_range
- Error messages now include context (book, set availability, etc.)
