fix: 修复钉钉应用内免登创建用户时未保存dingUserId导致无法发送钉钉通知的BUG

backend/src/main/java/com/designhub/service/UserService.java

@@ -635,6 +635,7 @@ public class UserService {
                 user.setRealName(name);
                 user.setEmail(email);
                 user.setAvatar(avatarUrl);
+                user.setDingUserId(dingtalkUserId); // 保存钉钉用户ID，用于发送钉钉通知
                 user.setCreateTime(LocalDateTime.now());
                 user.setUpdateTime(LocalDateTime.now());