Job Queue Metrics

Return a snapshot of job-queue observability metrics.<br><br>For the in-memory backend this exposes only backend and active_jobs.<br>For the Redis backend the snapshot also includes bridge counts, consumer<br>wrappers, cancel-dispatcher liveness, and the cancel-stats counters<br>(published / marker_hit / dispatched_owned /<br>dispatched_foreign / publish_errors / dispatcher_reconnects /<br>polling_watchdog_kills / activity_touch_errors /<br>activity_get_errors / activity_parse_errors /<br>dispatcher_internal_errors). dispatcher_reconnects tracks explicit<br>dispatcher-loop retries and redis-py transparent pubsub reconnect callbacks.<br><br>Restricted to superusers because the snapshot exposes process-wide tenant<br>activity (live job counts, cancel rates) — useful for ops, sensitive in<br>multi-tenant deployments.