Add turn configuration support for assistants

- Introduce a new `turnConfig` field in `AssistantConfig` and `Assistant` models to manage user interaction settings.
- Implement `TurnConfig`, `BargeInConfig`, `VadConfig`, and `TurnDetectionConfig` schemas to define turn management strategies.
- Update the backend to handle turn configuration in the database and during assistant operations.
- Enhance frontend components with a `TurnConfigEditor` for configuring turn settings, including VAD and barge-in strategies.
- Modify existing pages to integrate turn configuration, improving user experience and interaction capabilities.

backend/models.py

@@ -71,6 +71,7 @@ class AssistantConfig(BaseModel):
     tts_secrets: dict = {}
 
     enableInterrupt: bool = True
+    turnConfig: dict = Field(default_factory=dict)
 
     # Prompt assistant reusable tools. Execution remains type-specific in the pipeline.
     tools: list[RuntimeTool] = Field(default_factory=list)