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/schemas/app_schema.py

@@ -4,10 +4,6 @@ from typing import Optional, Any, List, Dict, Union
 from enum import Enum, StrEnum
 
 from pydantic import BaseModel, Field, ConfigDict, field_serializer, field_validator
-
-from app.schemas.workflow_schema import WorkflowConfigCreate
-
-
 # ---------- Multimodal File Support ----------
 
 class FileType(StrEnum):
@@ -317,7 +313,7 @@ class AppCreate(BaseModel):
     # only for type=multi_agent
     multi_agent_config: Optional[Dict[str, Any]] = None
 
-    workflow_config: Optional[WorkflowConfigCreate] = None
+    workflow_config: Optional[Dict[str, Any]] = None
 
 
 class AppUpdate(BaseModel):