feat(budget): 1회성 예산 API 추가

- BudgetOnetime 도메인/DTO/Mapper/Service 신규
- BudgetController: GET/POST/PUT/DELETE /api/account/budgets/onetime 엔드포인트 추가
- account.sql: budget_onetime 테이블 CREATE TABLE IF NOT EXISTS 추가
- WalletRequest: MINUS 유형 허용 추가
- CategoryService: importDefaults, validateParent, ensureCategory 추가

※ 최초 배포 시 서버 .env에 SQL_INIT_MODE=always 추가 후 재시작 필요 (budget_onetime 테이블 생성)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/main/resources/mapper/BudgetOnetimeMapper.xml

@@ -0,0 +1,60 @@
+<?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.BudgetOnetimeMapper">
+
+    <resultMap id="rm" type="com.sb.web.account.domain.BudgetOnetime">
+        <id  property="id"         column="id"/>
+        <result property="memberId"   column="member_id"/>
+        <result property="title"      column="title"/>
+        <result property="category"   column="category"/>
+        <result property="amount"     column="amount"/>
+        <result property="startDate"  column="start_date"/>
+        <result property="endDate"    column="end_date"/>
+        <result property="createdAt"  column="created_at"/>
+        <result property="updatedAt"  column="updated_at"/>
+    </resultMap>
+
+    <select id="findByMember" resultMap="rm">
+        SELECT id, member_id, title, category, amount, start_date, end_date, created_at, updated_at
+        FROM budget_onetime
+        WHERE member_id = #{memberId}
+        ORDER BY start_date DESC
+    </select>
+
+    <select id="findByIdAndMember" resultMap="rm">
+        SELECT id, member_id, title, category, amount, start_date, end_date, created_at, updated_at
+        FROM budget_onetime
+        WHERE id = #{id} AND member_id = #{memberId}
+    </select>
+
+    <!-- 기간 내 지출 합산 (category=null 이면 전체, 값 있으면 해당 카테고리만) -->
+    <select id="sumExpenseInRange" resultType="long">
+        SELECT COALESCE(SUM(amount), 0)
+        FROM account_entry
+        WHERE member_id = #{memberId}
+          AND type = 'EXPENSE'
+          AND entry_date BETWEEN #{startDate} AND #{endDate}
+          <if test="category != null and category != ''">
+            AND category = #{category}
+          </if>
+    </select>
+
+    <insert id="insert" parameterType="com.sb.web.account.domain.BudgetOnetime"
+            useGeneratedKeys="true" keyProperty="id">
+        INSERT INTO budget_onetime (member_id, title, category, amount, start_date, end_date, created_at, updated_at)
+        VALUES (#{memberId}, #{title}, #{category}, #{amount}, #{startDate}, #{endDate}, NOW(), NOW())
+    </insert>
+
+    <update id="update" parameterType="com.sb.web.account.domain.BudgetOnetime">
+        UPDATE budget_onetime
+        SET title = #{title}, category = #{category}, amount = #{amount},
+            start_date = #{startDate}, end_date = #{endDate}, updated_at = NOW()
+        WHERE id = #{id} AND member_id = #{memberId}
+    </update>
+
+    <delete id="delete">
+        DELETE FROM budget_onetime WHERE id = #{id} AND member_id = #{memberId}
+    </delete>
+
+</mapper>