feat(workflow): add opening statement and citation support

- Trigger opening statement on new conversation in run/run_stream
- Fix /opening endpoint to support workflow app type
- Fix features field missing in workflow config release snapshot
- Knowledge node returns citations alongside chunks
- Aggregate citations from all knowledge nodes in result builder
- Filter citations based on features.citation.enabled switch
- Fix WorkflowConfigCreate circular import in app_schema

api/app/utils/app_config_utils.py

@@ -153,7 +153,8 @@ def workflow_config_4_app_release(release: AppRelease) -> WorkflowConfig:
         edges=config_dict.get("edges", []),
         variables=config_dict.get("variables", []),
         execution_config=config_dict.get("execution_config", {}),
-        triggers=config_dict.get("triggers", [])
+        triggers=config_dict.get("triggers", []),
+        features=config_dict.get("features", {})
     )
 
     return config