Add brain memory services and APIs

Introduce the backend pieces for brain memory ingestion, routing, and
system telemetry so the new knowledge workflows can project data into a
brain view. The supporting tests lock in the new behavior and keep the
expanded backend surface stable.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/routers/conversation.py

@@ -92,11 +92,12 @@ async def chat(
 ):
     """简单版对话（非流式）"""
     agent_svc = AgentService(db)
-    conv_id, msg_id, content = await agent_svc.chat_simple(
+    conv_id, msg_id, content, model_name = await agent_svc.chat_simple(
         user_id=current_user.id,
         message=data.message,
         conversation_id=data.conversation_id,
         file_ids=data.file_ids,
+        model_name=data.model_name,
     )
 
     # 更新对话消息计数
@@ -111,6 +112,7 @@ async def chat(
         message_id=msg_id,
         content=content,
         agent_name="jarvis",
+        model_name=model_name,
     )
 
 
@@ -128,24 +130,24 @@ async def chat_stream(
             user_id=current_user.id,
             message=data.message,
             conversation_id=data.conversation_id,
+            file_ids=data.file_ids,
+            model_name=data.model_name,
         )
 
-        # 先发送元数据
         yield f"event: metadata\ndata: {json.dumps({'conversation_id': conv_id, 'message_id': msg_id})}\n\n"
 
-        # 流式发送内容
-        collected = ""
         try:
-            async for chunk in stream:
-                if chunk:
-                    collected += chunk
-                    yield f"event: chunk\ndata: {json.dumps({'content': chunk})}\n\n"
-
-            # 更新数据库中的消息
-            await agent_svc.save_response(msg_id, collected)
-
+            async for event in stream:
+                event_type = event.get('type', 'progress')
+                if event_type == 'chunk':
+                    yield f"event: chunk\ndata: {json.dumps({'content': event.get('content', '')}, ensure_ascii=False)}\n\n"
+                elif event_type == 'error':
+                    yield f"event: error\ndata: {json.dumps({'error': event.get('error', '未知错误')}, ensure_ascii=False)}\n\n"
+                else:
+                    payload = {k: v for k, v in event.items() if k != 'type'}
+                    yield f"event: progress\ndata: {json.dumps(payload, ensure_ascii=False)}\n\n"
         except Exception as e:
-            yield f"event: error\ndata: {json.dumps({'error': str(e)})}\n\n"
+            yield f"event: error\ndata: {json.dumps({'error': str(e)}, ensure_ascii=False)}\n\n"
         finally:
             yield f"event: done\ndata: {json.dumps({'message_id': msg_id})}\n\n"