Per-day availability time windows
Each day can now have different time windows — e.g., Monday 9:30-12:00 + 14:00-19:30, but Tuesday only 14:00-15:00.
Previously, all selected days shared the same time windows. Now the availability section uses a Cal.com-style per-day layout:
- Toggle each day on/off independently
- Add multiple time windows per day (morning + afternoon with lunch break)
- "Copy to all days" button for the common case where most days share the same schedule
- Fully backward-compatible — existing event types load their per-day rules correctly
The database schema was already designed for this (each availability_rules row has its own day_of_week). This release unlocks the full flexibility that was always there.