Replace hardcoded BullMQ job retention values (completed: 100 jobs / 1h, failed: 1000 jobs / 24h) with configurable env vars to prevent memory growth under load. Adds QUEUE_COMPLETED_RETENTION_COUNT, QUEUE_COMPLETED_RETENTION_AGE_S, QUEUE_FAILED_RETENTION_COUNT, and QUEUE_FAILED_RETENTION_AGE_S to orchestrator config. Defaults preserve existing behavior. Co-Authored-By: Claude Opus 4.6 <[email protected]>