- Add job queue system to ensure only one update runs at a time
- Add Server-Sent Events (SSE) for real-time push updates
- Increase rate limit from 20/min to 60/min for update endpoints
- Add unit tests for queue and SSE functionality
- Frontend: Update modal now uses SSE with polling fallback
Eliminates: 429 rate limit errors, duplicate modals, race conditions
Related to #671