- Device-status panel (DeviceStatusController): site-scoped liveness over stored
heartbeat telemetry. Fix config_drift false-positive by storing NULL until the
device actually reports a version (was firing "설정 미적용" on every device).
- Zone save rejects a blank/unknown device_id (DeviceRepository::exists) so a zone
is never persisted against a device that will never fetch it.
- Snapshot proxy sends immutable private cache headers, ending the 5s-poll
re-download of every thumbnail (a Cafe24 traffic-cap hazard).
- Event list: paged-in acknowledgements stick; honesty affordances for the paging
gap, a stale device poll, and a filtered camera aging out; logout wired for
every page via the shared layout.
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