feat: project skeleton + DB migrations V1-V12 + ga-common framework

- Gradle multi-module: ga-common, ga-core, ga-api, ga-batch, ga-admin
- Flyway V1-V12: org/product/rule/receive/ledger/settle/batch/code/menu/system + seed
- ga-common (complete):
  - model: ApiResponse, PageResponse, SearchParam, TreeNode
  - exception: ErrorCode, BizException, GlobalExceptionHandler
  - annotation + aop: @RequirePermission, @DataChangeLog, ApiLog
  - auth + security: JWT, SecurityConfig
  - mybatis: BaseMapper, EncryptTypeHandler, JsonTypeHandler, AuditInterceptor
  - code (Redis cached) / menu (RBAC tree) / file / system / notification
  - excel: SXSSF+Cursor export, SAX+batch import (1M/700K rows)
  - util: Date/Money/Mask/Encrypt/Security

ga-common/src/main/java/com/ga/common/menu/MenuMapper.java

@@ -0,0 +1,32 @@
+package com.ga.common.menu;
+
+import org.apache.ibatis.annotations.Mapper;
+import org.apache.ibatis.annotations.Param;
+
+import java.util.List;
+import java.util.Map;
+
+@Mapper
+public interface MenuMapper {
+
+    /** 전체 활성 메뉴 (정렬됨) */
+    List<MenuVO> selectAllActive();
+
+    /** 사용자가 접근 가능한 메뉴 목록 */
+    List<MenuVO> selectAccessibleMenusByUserId(@Param("userId") Long userId);
+
+    /** 사용자별 (menuId → permCodes) 매핑 */
+    List<Map<String, Object>> selectUserPermissions(@Param("userId") Long userId);
+
+    /** 단일 (menuCode, permCode) 권한 보유 여부 */
+    int hasPermission(@Param("userId") Long userId,
+                      @Param("menuCode") String menuCode,
+                      @Param("permCode") String permCode);
+
+    MenuVO selectById(@Param("menuId") Long menuId);
+    MenuVO selectByCode(@Param("menuCode") String menuCode);
+    int insert(MenuVO vo);
+    int update(MenuVO vo);
+    int deleteById(@Param("menuId") Long menuId);
+    int countChildren(@Param("menuId") Long menuId);
+}