feat: 가계부·게시판 백엔드 API 구현

- com.sb.web 패키지로 재구성: account / auth / board / user / admin / common
- 가계부(account): 내역(필터), 계좌·순자산, 예산, 분류, 정기 거래, 투자 포트폴리오
  (종목·매매 이력, 이동평균 평단·실현/평가손익)
- MyBatis + MariaDB + Redis 세션, BCrypt
- 스키마 자동 초기화(db/*.sql, 멱등), 사용자별 데이터 격리(member_id)
- 문서: docs/BACKEND.md, .env.example

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

src/main/resources/mapper/WalletMapper.xml

@@ -0,0 +1,73 @@
+<?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.WalletMapper">
+
+    <resultMap id="walletResultMap" type="com.sb.web.account.domain.Wallet">
+        <id property="id" column="id"/>
+        <result property="memberId" column="member_id"/>
+        <result property="type" column="type"/>
+        <result property="name" column="name"/>
+        <result property="issuer" column="issuer"/>
+        <result property="accountNumber" column="account_number"/>
+        <result property="cardType" column="card_type"/>
+        <result property="openingBalance" column="opening_balance"/>
+        <result property="openingDate" column="opening_date"/>
+        <result property="currentValue" column="current_value"/>
+        <result property="createdAt" column="created_at"/>
+        <result property="updatedAt" column="updated_at"/>
+    </resultMap>
+
+    <sql id="cols">id, member_id, type, name, issuer, account_number, card_type,
+        opening_balance, opening_date, current_value, created_at, updated_at</sql>
+
+    <select id="findByMember" parameterType="long" resultMap="walletResultMap">
+        SELECT <include refid="cols"/> FROM wallet
+        WHERE member_id = #{memberId}
+        ORDER BY type, name
+    </select>
+
+    <select id="findByIdAndMember" resultMap="walletResultMap">
+        SELECT <include refid="cols"/> FROM wallet
+        WHERE id = #{id} AND member_id = #{memberId}
+    </select>
+
+    <insert id="insert" parameterType="com.sb.web.account.domain.Wallet"
+            useGeneratedKeys="true" keyProperty="id">
+        INSERT INTO wallet (member_id, type, name, issuer, account_number, card_type,
+                            opening_balance, opening_date, current_value, created_at, updated_at)
+        VALUES (#{memberId}, #{type}, #{name}, #{issuer}, #{accountNumber}, #{cardType},
+                #{openingBalance}, #{openingDate}, #{currentValue}, NOW(), NOW())
+    </insert>
+
+    <update id="update" parameterType="com.sb.web.account.domain.Wallet">
+        UPDATE wallet
+        SET type = #{type}, name = #{name}, issuer = #{issuer},
+            account_number = #{accountNumber}, card_type = #{cardType},
+            opening_balance = #{openingBalance}, opening_date = #{openingDate},
+            current_value = #{currentValue}
+        WHERE id = #{id} AND member_id = #{memberId}
+    </update>
+
+    <!-- 계좌별 현재 잔액 = 초기잔액 + 수입 - 지출 - 이체출금 + 이체입금 -->
+    <select id="findBalances" parameterType="long" resultType="map">
+        SELECT w.id AS id,
+            w.opening_balance
+            + COALESCE((SELECT SUM(e.amount) FROM account_entry e
+                        WHERE e.member_id = w.member_id AND e.type = 'INCOME'  AND e.wallet_id = w.id), 0)
+            - COALESCE((SELECT SUM(e.amount) FROM account_entry e
+                        WHERE e.member_id = w.member_id AND e.type = 'EXPENSE' AND e.wallet_id = w.id), 0)
+            - COALESCE((SELECT SUM(e.amount) FROM account_entry e
+                        WHERE e.member_id = w.member_id AND e.type = 'TRANSFER' AND e.wallet_id = w.id), 0)
+            + COALESCE((SELECT SUM(e.amount) FROM account_entry e
+                        WHERE e.member_id = w.member_id AND e.type = 'TRANSFER' AND e.to_wallet_id = w.id), 0)
+            AS balance
+        FROM wallet w
+        WHERE w.member_id = #{memberId}
+    </select>
+
+    <delete id="delete">
+        DELETE FROM wallet WHERE id = #{id} AND member_id = #{memberId}
+    </delete>
+
+</mapper>