feat: add batch operations for forwards, tunnels, and nodes

- Add batch delete, redeploy, and change-tunnel for forwards
- Add batch delete and redeploy for tunnels
- Add batch delete for nodes
- Add multi-select UI with floating toolbar on all three pages
- Create DTOs: BatchDeleteDto, BatchRedeployDto, BatchChangeTunnelDto, BatchOperationResultDto

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

@@ -0,0 +1,16 @@
+package com.admin.common.dto;
+
+import lombok.Data;
+import javax.validation.constraints.NotEmpty;
+import javax.validation.constraints.NotNull;
+import java.util.List;
+
+@Data
+public class BatchChangeTunnelDto {
+    
+    @NotEmpty(message = "转发ID列表不能为空")
+    private List<Long> forwardIds;
+    
+    @NotNull(message = "目标隧道ID不能为空")
+    private Long targetTunnelId;
+}