feat: 데이터 가져오기(복구) — 엑셀 백업으로 전체 교체 (트랜잭션)

- POST /api/account/restore: 기존 데이터 전부 삭제 후 이름 기준 재생성
  (계좌→태그→분류(대/소)→내역→고정→예산→자주내역), 한 트랜잭션(실패 시 롤백)
- 빈 데이터 안전장치, 투자 종목/매매는 복구 대상 외(삭제됨)
- BackupMapper(deleteByMember), RestoreRequest DTO, BackupService/Controller

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

src/main/resources/mapper/BackupMapper.xml

@@ -0,0 +1,41 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
+        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
+<mapper namespace="com.sb.web.account.mapper.BackupMapper">
+
+    <delete id="deleteEntryTags">
+        DELETE FROM account_entry_tag
+        WHERE entry_id IN (SELECT id FROM account_entry WHERE member_id = #{memberId})
+    </delete>
+    <delete id="deleteEntries">
+        DELETE FROM account_entry WHERE member_id = #{memberId}
+    </delete>
+    <delete id="deleteRecurrings">
+        DELETE FROM recurring WHERE member_id = #{memberId}
+    </delete>
+    <delete id="deleteBudgets">
+        DELETE FROM budget WHERE member_id = #{memberId}
+    </delete>
+    <delete id="deleteBudgetIncome">
+        DELETE FROM budget_income WHERE member_id = #{memberId}
+    </delete>
+    <delete id="deleteQuickEntries">
+        DELETE FROM quick_entry WHERE member_id = #{memberId}
+    </delete>
+    <delete id="deleteInvestTrades">
+        DELETE FROM invest_trade WHERE member_id = #{memberId}
+    </delete>
+    <delete id="deleteInvestHoldings">
+        DELETE FROM invest_holding WHERE member_id = #{memberId}
+    </delete>
+    <delete id="deleteCategories">
+        DELETE FROM account_category WHERE member_id = #{memberId}
+    </delete>
+    <delete id="deleteTags">
+        DELETE FROM account_tag WHERE member_id = #{memberId}
+    </delete>
+    <delete id="deleteWallets">
+        DELETE FROM wallet WHERE member_id = #{memberId}
+    </delete>
+
+</mapper>