Expand description
Scheduled interval snapshots. On each tick the scheduler fires any due snapshot_schedule
(enabled, and either never fired or its interval has elapsed since last_fired_at): it grabs a
live JPEG via the snapshot service, writes it to snapshots_dir/{camera_id}/{taken_at}.jpg,
records a snapshots row, and advances last_fired_at. Captured frames are pruned by the
retention sweeper past HELDAR_SNAPSHOT_RETENTION_HOURS. Spawned from main (supervised) only
when HELDAR_SNAPSHOT_SCHEDULER_ENABLED.