feat: 新增三角洲改枪码模块

- 新增 DeltaGunCode 实体/Mapper/Service/Controller（分页列表、新增、更新、删除）
- WebSecurityConfig 放行 /delta-gun-code/public/**，公开页免登录访问
- 附建表与菜单权限 SQL：sql/delta_gun_code.sql

src/main/java/com/freedom/admin/service/DeltaGunCodeService.java

@@ -0,0 +1,13 @@
+package com.freedom.admin.service;
+
+import com.baomidou.mybatisplus.extension.service.IService;
+import com.freedom.admin.entity.DeltaGunCode;
+
+/**
+ * 业务层-三角洲改枪码表
+ *
+ * @author zhangjiaxun
+ */
+public interface DeltaGunCodeService extends IService<DeltaGunCode> {
+
+}

src/main/java/com/freedom/admin/service/impl/DeltaGunCodeServiceImpl.java

@@ -0,0 +1,19 @@
+package com.freedom.admin.service.impl;
+
+import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
+import com.freedom.admin.entity.DeltaGunCode;
+import com.freedom.admin.mapper.DeltaGunCodeMapper;
+import com.freedom.admin.service.DeltaGunCodeService;
+import lombok.extern.log4j.Log4j2;
+import org.springframework.stereotype.Service;
+
+/**
+ * 业务层实现-三角洲改枪码表
+ *
+ * @author zhangjiaxun
+ */
+@Service
+@Log4j2
+public class DeltaGunCodeServiceImpl extends ServiceImpl<DeltaGunCodeMapper, DeltaGunCode> implements DeltaGunCodeService {
+
+}