Add DashScope ASR model support and enhance related components

- Introduced DashScope as a new ASR model in the database initialization.
- Updated ASRModel schema to include vendor information.
- Enhanced ASR router to support DashScope-specific functionality, including connection testing and preview capabilities.
- Modified frontend components to accommodate DashScope as a selectable vendor with appropriate default settings.
- Added tests to validate DashScope ASR model creation, updates, and connectivity.
- Updated backend API to handle DashScope-specific base URLs and vendor normalization.

api/app/schemas.py

@@ -191,6 +191,7 @@ class ASRModelCreate(ASRModelBase):
 
 class ASRModelUpdate(BaseModel):
     name: Optional[str] = None
+    vendor: Optional[str] = None
     language: Optional[str] = None
     base_url: Optional[str] = None
     api_key: Optional[str] = None