feat: add backfill resume support and session/retry fixes for VODs

feat: throttle VOD resolution checks to 5m and auto-complete streams older than 3 hours with no VOD

feat: automatic VOD ID resolution for stream sessions and historical pending streams

feat: smart gap detection and user roles sync backfill improvements

feat: smart gap detection with coverage windows - track exact time ranges captured per stream

feat: worker and chat_mod_worker now also sync roles to /api/log/roles on every message batch

feat: global roles migration, VIP badges, role backfiller script

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

Optimize moderation logging: fix duplicate collisions, auto-refresh streamer OAuth tokens, and implement IRC keep-alive timeouts. Add unit tests.

feat: tune Whisper settings and add word mappings

fix: adjust Whisper parameters to disable temperature fallback and prevent hallucinations on silence/noise

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