- T55: Setup APScheduler with AsyncIOScheduler and @scheduled_job decorator
- T56: Implement hourly usage stats sync from OpenRouter API
- T57: Implement daily API key validation job
- T58: Implement weekly cleanup job for old usage stats
- Add usage_stats_retention_days config option
- Integrate scheduler with FastAPI lifespan events
- Add 26 unit tests for scheduler, sync, and cleanup tasks
- Add apscheduler to requirements.txt
The background tasks now automatically:
- Sync usage stats every hour from OpenRouter
- Validate API keys daily at 2 AM UTC
- Clean up old data weekly on Sunday at 3 AM UTC
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