chore: cleanup test scripts, secure deployment script, and implement Voice/TTS frontend refinements ...

- Removed all temporary root Python test scripts
- Secured remote_deploy.sh credentials using environment variables
- Added data/audio payloads directory to .gitignore
- Added automatic DB migration script (migrate.py) via uvicorn lifespan
- Applied major refactors to UI Voice Chat, Session handling, and unified React API configs
- Updated models and dependencies natively syncing with Nginx proxy features

docs: add deployment reference and deploy scripts ...

- Add docs/deployment_reference.md with complete proxy architecture
- Add .agent/workflows/deploy_to_production.md and envoy_control_plane.md
- Add remote_deploy.sh for 1-click CI/CD
- Fix Nginx websocket Upgrade maps and connection closures
- Update ai-hub Dockerfile to handle proxy headers
- Update local_deployment.sh and docker-compose.yml