f8f209dcba
- Migration 005: schedule_entries table (date TEXT UNIQUE, one person per day)
- POST /api/schedule — assign user to one or more dates in a single
transaction; any date conflict rejects the whole request (409)
- GET /api/schedule — list all entries ordered by date, optional ?from/?to
- GET /api/schedule/current — today's on-call user (UTC date), 404 if none
- DELETE /api/schedule/{id} — remove an entry (204)