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/db/models.py

@@ -108,6 +108,7 @@ class Assistant(Base):
     runtime_mode: Mapped[str] = mapped_column(String(16), default="pipeline")
     greeting: Mapped[str] = mapped_column(String(2048), default="")
     enable_interrupt: Mapped[bool] = mapped_column(Boolean, default=True)
+    turn_config: Mapped[dict] = mapped_column(JSON, default=dict)
     vision_enabled: Mapped[bool] = mapped_column(Boolean, default=False)
     vision_model_resource_id: Mapped[str | None] = mapped_column(
         String(40),