fix: implement system-settings fallback in STT/TTS routes and resolve missing key 500 error

fix: resolve 'no active stt provider' by ensuring global settings fallback even without user preferences

debug: add verbose TTS logging and strict concurrency of 1 to isolate Google 500 errors

fix: improve LLM error reporting and validate keys early

fix: resolve stale LLM config and persist provider settings to YAML

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

feat: expose model info to users, multi-model provider cloning, cleaner profile UI ...

- Show model name under each provider button for all users (ProfilePage)
- Admin Settings: upgraded 'Register New Instance' panel with 4 fields:
  provider type, label suffix (with model-name hint), pre-set model
  dropdown, and 'Inherit API Key From' for same-type instance cloning
- Fix API key inheritance: use _clone_from marker instead of copying
  masked key; backend resolves real key from DB before saving
- Lock cloned-key instances: API key field is greyed out with lock icon
  and 'Inherited from <source>' display; Unlink button breaks the link
- Provider card header: show configured model name instead of
  'User Override / System Provided' labels
- ProfilePage: remove confusing 'Do Extra Work' override panel entirely;
  ServiceSelect is now a clean provider selector with no hidden admin UI
- SettingsPage: remove 'User Override' / 'System Provided' badge

Refactor STT model selection to dropdown, add YAML config import/export, and refine Voice/Coding Assistant UI

feat: Add new session UI, token counter, load history, and session isolation

fix: remove forced sessionId reset in websocket service

fix test error

refactor the coding workspace && support larger code refactoring request

fix test code

improve & fix bugs

implement core func for coding assistant

use litellm underlying

add chinese voice if detecting chinese

add gcloud_tts

introduce gcloud tts

fix typo

include stt integration test

introduce stt endpoint

add stt support

add tts support from user end

refactor the integration test but tts is broken

expose ttls model for external configuration

introduce gemini tts model into the system

add support for multi-models