Add vision model support and related configurations in Assistant

- Introduce new fields in AssistantConfig, schemas, and database models to support vision capabilities, including `vision_enabled` and `vision_model_resource_id`.
- Enhance validation logic in routes to ensure proper handling of vision models and their requirements.
- Update the AssistantPage and related frontend components to include options for enabling vision understanding and selecting appropriate vision models.
- Modify database seed scripts to include vision-related data for assistants, ensuring consistent setup.
- Refactor related functions to integrate vision model handling in the audio-visual processing pipeline.

backend/schemas.py

@@ -52,6 +52,8 @@ class AssistantUpsert(CamelModel):
     runtime_mode: RuntimeMode = "pipeline"
     greeting: str = ""
     enable_interrupt: bool = True
+    vision_enabled: bool = False
+    vision_model_resource_id: str | None = None
 
     model_resource_ids: dict[ModelType, str] = Field(default_factory=dict)
     knowledge_base_id: str | None = None