- Add POST /calendar/slots/{slot_id}/cancel for real slot cancellation
- Add POST /calendar/slots/virtual/{virtual_id}/cancel for virtual slot cancellation
- Virtual cancel materializes the slot first, then marks as Skipped
- Both endpoints enforce past-slot immutability guard
- Both endpoints detach from plan (set plan_id=NULL)
- Status set to SlotStatus.SKIPPED on cancel
- Add TimeSlotCancelResponse schema
- Add TimeSlotEdit schema (partial update, all fields optional)
- Add TimeSlotEditResponse schema
- Add PATCH /calendar/slots/{slot_id} for editing real slots
- Add PATCH /calendar/slots/virtual/{virtual_id} for editing virtual slots
- Triggers materialization before applying edits
- Detaches from plan after edit
- Both endpoints enforce past-slot immutability, overlap detection, plan
detachment, and workload warnings
- Add GET /calendar/day endpoint with optional ?date= query param
- Returns unified CalendarDayResponse merging real slots + virtual plan slots
- New CalendarSlotItem schema supports both real (id) and virtual (virtual_id) slots
- Excludes inactive slots (skipped/aborted) from results
- All slots sorted by scheduled_at ascending
- Helper functions for real/virtual slot conversion