Add schedule slots engine (time-based and event-based scheduling)

[Alex1981-tech]

Summary

Implements a schedule slot system that enables time-of-day and event-based content scheduling for Anthias, as proposed in #2671.

When ScheduleSlot records exist the viewer switches to "schedule mode": only assets linked to the currently-active slot are played. When the table is empty the viewer falls back to legacy behaviour (asset.is_active()) — full backward compatibility is preserved.

Key features

• Three slot types: default (fallback), time (daily time window), event (one-time/recurring)
• Slot priority: event > time > default — higher-priority slots override lower ones
• Overnight slots: e.g. 22:00→06:00, days_of_week refers to the start day
• Event modes: one-time (specific date), daily (date range), weekly (selected days)
• No-loop mode: event slots play their content once, then resume normal schedule
• Deadline timer: threading.Timer interrupts current asset for on-time slot transitions
• Duration override: per-slot-item override of asset duration
• Time overlap validation: prevents conflicting time slots on shared days
• REST API: full CRUD for slots and items, reorder endpoint, schedule status endpoint
• OpenAPI schema: all endpoints decorated with @extend_schema

Files changed

File	Change
anthias_app/models.py	+ScheduleSlot, ScheduleSlotItem models (~170 lines)
anthias_app/migrations/0003_schedule_slots.py	Migration for both new tables
viewer/scheduling.py	Schedule-aware playlist generation + deadline timer in Scheduler
api/serializers/schedule.py	4 serializers with overlap/default validation
api/views/schedule.py	6 API view classes with @extend_schema
api/urls/v2.py	+6 schedule endpoint routes
anthias_app/admin.py	Admin for ScheduleSlot + ScheduleSlotItem inline
tests/test_scheduler.py	Updated for 4-tuple return + new schedule mode tests
api/tests/test_schedule_endpoints.py	API endpoint tests (CRUD, reorder, status)

API endpoints

GET    /api/v2/schedule/slots                          — List all slots
POST   /api/v2/schedule/slots                          — Create slot
GET    /api/v2/schedule/slots/<slot_id>                 — Get slot
PUT    /api/v2/schedule/slots/<slot_id>                 — Update slot
DELETE /api/v2/schedule/slots/<slot_id>                 — Delete slot
GET    /api/v2/schedule/slots/<slot_id>/items           — List slot items
POST   /api/v2/schedule/slots/<slot_id>/items           — Add asset to slot
PUT    /api/v2/schedule/slots/<slot_id>/items/<item_id> — Update item
DELETE /api/v2/schedule/slots/<slot_id>/items/<item_id> — Delete item
POST   /api/v2/schedule/slots/<slot_id>/items/order     — Reorder items
GET    /api/v2/schedule/status                          — Current schedule status

How it works

1. generate_asset_list() now returns a 4-tuple: (playlist, deadline, no_loop, active_slot_id)
2. If no ScheduleSlot records exist → legacy path (unchanged)
3. If slots exist → find active slot by priority → build playlist from ScheduleSlotItems
4. Scheduler class extended with deadline timer, no-loop support, and event completion handling

Backward compatibility

• Zero slots = original behaviour — no database records needed, no migration side effects
• generate_asset_list() returns 4-tuple but legacy callers only need to update unpacking
• All existing tests updated and passing
• No changes to viewer/__init__.py or viewer/media_player.py

Test plan

• ruff check passes on all changed files
• ruff format --check passes on all changed files
• python manage.py makemigrations --check — migration is up to date
• python manage.py test tests.test_scheduler — scheduler tests pass
• python manage.py test api.tests.test_schedule_endpoints — API tests pass
• Manual test: create default slot via API, verify viewer plays its assets
• Manual test: create time slot, verify it activates/deactivates at correct times
• Manual test: verify legacy mode (delete all slots) still works

Closes #2671

🤖 Generated with Claude Code

[sonarqubecloud]

Quality Gate passed

Issues
8 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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