refactor(llm): 优化对话控制器中的流式聊天方法

- 将 void 返回类型改为 SseEmitter，以正确表示流式响应
- 添加返回值，确保客户端

yudao-module-llm/yudao-module-llm-biz/src/main/java/cn/iocoder/yudao/module/llm/controller/admin/conversation/ConversationController.java

@@ -110,7 +110,7 @@ public class ConversationController {
      * @return SseEmitter 对象，用于流式发送响应
      */
     @PostMapping("/stream-chat")
-    public void streamChat (@Valid @RequestBody ChatReqVO chatReqVO, HttpServletResponse response) {
+    public SseEmitter streamChat (@Valid @RequestBody ChatReqVO chatReqVO, HttpServletResponse response) {
         log.info("收到对话推理请求，请求参数: {}", chatReqVO);
         SseEmitter emitter = new SseEmitter(120_000L);
 //        ExecutorService executor = Executors.newSingleThreadExecutor();
@@ -147,6 +147,7 @@ public class ConversationController {
                 }
             }
         });
+        return emitter;
     }
 
     @PostMapping("/text-to-image")