start_transcription() blocks up to 15s waiting for the Deepgram
WebSocket to connect. Running it synchronously in the async endpoint
blocked the entire uvicorn event loop, preventing:
- pollStatus from completing (frozen HTTP request)
- WebSocket broadcasts from being sent
- Any other API requests from being handled
Fix: run start/stop/reload in thread pool via run_in_executor so
the event loop stays responsive during long-running operations.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
ae61c8c75a