Job Queue Metrics

Return a snapshot of job-queue observability metrics.

For the in-memory backend this exposes only backend and active_jobs. For the Redis backend the snapshot also includes bridge counts, consumer wrappers, cancel-dispatcher liveness, and the cancel-stats counters (published / marker_hit / dispatched_owned / dispatched_foreign / publish_errors / dispatcher_reconnects / polling_watchdog_kills / activity_touch_errors / activity_get_errors / activity_parse_errors / dispatcher_internal_errors). dispatcher_reconnects tracks explicit dispatcher-loop retries and redis-py transparent pubsub reconnect callbacks.

Restricted to superusers because the snapshot exposes process-wide tenant activity (live job counts, cancel rates) — useful for ops, sensitive in multi-tenant deployments.