Integrate stream-start and stream-end signaling in worker.py and add /api/log/stream-start endpoint.

feat: map truncated 'кримб' to 'кримбр'

feat: add more synonyms for кримбр

feat: tune Whisper settings and add word mappings

security: sync CORS and error handling security updates in main repo

feat: implement caching, rate limiter, and security headers (CSP) for decoupled deploy

chore: handle missing client dist path gracefully in server

chore: disable EventSub listener in server

feat: prepare transition to decoupled hosting (Render + Netlify + Supabase)