feat: 회원 탈퇴(자기 계정 삭제) — Play 정책 대응

- DELETE /api/auth/me: 본인 계정과 모든 데이터 영구 삭제
- 게시판(글/댓글/추천/이미지)·가계부 전체·포인트·결제기록·세션 → 회원 순 삭제
- WithdrawMapper(게시판/포인트/결제/세션) + BackupMapper(가계부) 재사용
- AuthServiceTest 생성자 보강

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/test/java/com/sb/web/auth/service/AuthServiceTest.java

@@ -47,12 +47,15 @@ class AuthServiceTest {
     @Mock ValueOperations<String, Object> valueOps;
     @Mock AppSettingService appSettingService;
     @Mock AuthSessionMapper authSessionMapper;
+    @Mock com.sb.web.auth.mapper.WithdrawMapper withdrawMapper;
+    @Mock com.sb.web.account.mapper.BackupMapper backupMapper;
 
     AuthService service;
 
     @BeforeEach
     void setUp() {
-        service = new AuthService(memberMapper, passwordEncoder, redisTemplate, appSettingService, authSessionMapper);
+        service = new AuthService(memberMapper, passwordEncoder, redisTemplate, appSettingService, authSessionMapper,
+                withdrawMapper, backupMapper);
     }
 
     private Member localMember() {