TODO: Deferred transmissions

Creates VOD archives when devices go offline, stored for later retrieval.

archives/{session_id}/
├── segments/
│   ├── seg_000100.ts
│   └── ...
└── playlist.m3u8

Archives are tracked in PostgreSQL deferred_transmissions table.

Archives are deleted after ARCHIVE_RETENTION_DAYS (default: 7 days).

• src/stream_processor/service/archive_service.py