Refactor backend configuration management and update environment settings

- Replace the `config.py` module with a new `settings.py` to streamline environment variable management, focusing on database, CORS, and TURN settings.
- Update references throughout the backend codebase to use the new `settings` module instead of the deprecated `config`.
- Modify the `.env.example` file to reflect the new configuration approach, indicating that model provider credentials should be maintained separately.
- Enhance the `AssistantConfig` model to clarify the source of runtime connection information, ensuring it is injected from model resources rather than relying on defaults from the environment.
- Introduce new user scripts for audio and video management in the Tampermonkey environment, enhancing WebRTC capabilities.

backend/migrations/env.py

@@ -7,7 +7,7 @@ from sqlalchemy import pool
 from sqlalchemy.engine import Connection
 from sqlalchemy.ext.asyncio import async_engine_from_config
 
-import config as app_config
+import settings as app_settings
 from db.models import Base
 
 config = context.config
@@ -19,7 +19,7 @@ target_metadata = Base.metadata
 
 
 def get_url() -> str:
-    return app_config.DATABASE_URL
+    return app_settings.DATABASE_URL
 
 
 def run_migrations_offline() -> None: