fix(workflow): add reasoning content, suggested questions, citations and audio status support

- Introduce `reasoning_content`, `suggested_questions`, `citations`, and `audio_status` fields in conversation and app response schemas
- Conditionally set `audio_status` to `"pending"` only when `audio_url` is present
- Replace `model_dump` override with `@model_serializer(mode="wrap")` for cleaner serialization logic
- Change knowledge base validation failure from `RuntimeError` to warning + `continue` to avoid halting retrieval on invalid KB

api/app/core/workflow/nodes/knowledge/node.py

@@ -334,7 +334,8 @@ class KnowledgeRetrievalNode(BaseNode):
             for kb_config in knowledge_bases:
                 db_knowledge = knowledge_repository.get_knowledge_by_id(db=db, knowledge_id=kb_config.kb_id)
                 if not (db_knowledge and db_knowledge.chunk_num > 0 and db_knowledge.status == 1):
-                    raise RuntimeError("The knowledge base does not exist or access is denied.")
+                    logger.warning("The knowledge base does not exist or access is denied.")
+                    continue
                 tasks.append(self.knowledge_retrieval(db, query, db_knowledge, kb_config))
             if tasks:
                 result = await asyncio.gather(*tasks)