feat(backend): enhance task and schedule center APIs with expanded endpoints

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

backend/app/routers/conversation.py

@@ -100,6 +100,7 @@ async def chat(
             conversation_id=data.conversation_id,
             file_ids=data.file_ids,
             model_name=data.model_name,
+            runtime=data.runtime,
         )
     except ValueError as exc:
         raise HTTPException(status_code=400, detail=str(exc))
@@ -115,7 +116,7 @@ async def chat(
         conversation_id=conv_id,
         message_id=msg_id,
         content=content,
-        agent_name="jarvis",
+        agent_name=data.runtime or "jarvis",
         model_name=model_name,
     )
 
@@ -141,6 +142,7 @@ async def chat_stream(
                     conversation_id=data.conversation_id,
                     file_ids=data.file_ids,
                     model_name=data.model_name,
+                    runtime=data.runtime,
                 )
             except ValueError as exc:
                 yield f"event: error\ndata: {json.dumps({'error': str(exc)}, ensure_ascii=False)}\n\n"