服务层重构与优化：补全所有ServiceImpl实现类，修复RestTemplate注入，完善DTO与配置，保证编译与启动通过

backend-single/src/main/java/com/emotion/dto/response/GuestChatResponse.java

@@ -0,0 +1,35 @@
+package com.emotion.dto.response;
+
+import lombok.Data;
+import lombok.EqualsAndHashCode;
+
+/**
+ * 访客聊天响应类
+ * 
+ * @author emotion-museum
+ * @date 2025-07-24
+ */
+@Data
+@EqualsAndHashCode(callSuper = true)
+public class GuestChatResponse extends BaseResponse {
+    
+    /**
+     * 消息内容
+     */
+    private String message;
+    
+    /**
+     * 消息ID
+     */
+    private String messageId;
+    
+    /**
+     * 时间戳
+     */
+    private Long timestamp;
+    
+    /**
+     * 是否有错误
+     */
+    private Boolean error;
+}