**Problem:** Each dashboard/engine project consumer polled
`task_deleted` outbox on a fixed 5s setInterval, so ~44 per-project
consumers thundered together on the same cadence — an idle DB query
storm and CPU hot-spot even when projects were paused/idle.
**Fix:** The outbox consumer reschedules itself from each poll outcome:
an idle poll (zero events) grows the next delay by
`TASK_DELETED_OUTBOX_BACKOFF_STEP_MS` toward `MAX_POLL_MS`, with ±20%
jitter so the consumers de-synchronize; a poll that delivered events
resets to the fast base. A paused/idle project drains its outbox and
backoff alone drops the DB load.
**Includes:** regression test (bounded jitter + idle growth),
performance changeset, solution doc, deploy handoff script.
<!-- This is an auto-generated comment: release notes by coderabbit.ai
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## Summary by CodeRabbit
- **Performance**
- Reduced unnecessary idle polling by gradually increasing the polling
interval, up to 60 seconds, with bounded timing variation.
- Restored the faster 5-second polling cadence when new events, waits,
or transient errors occur.
- Preserved event ordering, delivery guarantees, acknowledgements, and
independent behavior across concurrent consumers.
- **Documentation**
- Added guidance on polling behavior, deployment verification, and
monitoring targets.
- **Tests**
- Added coverage for backoff growth, jitter limits, event bursts,
concurrent consumers, error handling, retries, and clean shutdown.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
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