fix: 为嵌套的TunnelAssignItem添加@Valid注解确保校验生效

springboot-backend/src/main/java/com/admin/common/dto/UserTunnelBatchAssignDto.java

@@ -1,6 +1,7 @@
 package com.admin.common.dto;
 
 import lombok.Data;
+import javax.validation.Valid;
 import javax.validation.constraints.NotNull;
 import javax.validation.constraints.NotEmpty;
 import java.util.List;
@@ -11,6 +12,7 @@ public class UserTunnelBatchAssignDto {
     @NotNull(message = "用户ID不能为空")
     private Integer userId;
     
+    @Valid
     @NotEmpty(message = "隧道列表不能为空")
     private List<TunnelAssignItem> tunnels;