Routes: channel + playlist CRUD, start/stop/play/pause/skip transport, as-run
log. RBAC via assertProjectAccess on channel.project_id; null project ⇒
admin-only (recorder convention).
Sidecar orchestration mirrors recorders.js: Docker socket for local node,
node-agent /sidecar/start for remote. Channel start passes CHANNEL_ID env so
the sidecar can write HLS preview to /media/live/<id>.
DeckLink port-contention guard: blocks starting a decklink channel when a
recorder or another channel on the same node+device_index is active.
restartChannel(id) helper picks another healthy cluster node and re-places
non-decklink channels; decklink is alert-only. Exposed for the scheduler.
Scheduler tick adds step 6: poll each running channel's sidecar /status,
update last_heartbeat_at, and after ~3 misses trigger restartChannel +
self-call /start. Reuses the existing PG advisory lock so multi-replica
deploys don't double-fire failovers.
