feat: 월별 예산 + 전월/다음달 복사

- budget 테이블에 year/month 추가, (member,category)→(member,category,year,month) 유니크 교체
  기존 상시 예산은 현재 월로 1회 이관
- 예산 조회/생성/현황/기간차트를 월별로(findByMember에 year/month)
- copyMonth: 다른 월 예산을 대상 월로 복사(같은 분류 덮어씀) + POST /budgets/copy
- 백업 복구 시 예산은 현재 월로 등록

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

src/main/resources/mapper/BudgetMapper.xml

@@ -14,15 +14,19 @@
         <result property="weekly" column="weekly"/>
         <result property="monthly" column="monthly"/>
         <result property="yearly" column="yearly"/>
+        <result property="year" column="year"/>
+        <result property="month" column="month"/>
         <result property="createdAt" column="created_at"/>
         <result property="updatedAt" column="updated_at"/>
     </resultMap>
 
     <sql id="cols">id, member_id, category, fixed, base_unit, base_amount,
-        daily, weekly, monthly, yearly, created_at, updated_at</sql>
+        daily, weekly, monthly, yearly, `year`, `month`, created_at, updated_at</sql>
 
-    <select id="findByMember" parameterType="long" resultMap="budgetResultMap">
-        SELECT <include refid="cols"/> FROM budget WHERE member_id = #{memberId} ORDER BY category
+    <select id="findByMember" resultMap="budgetResultMap">
+        SELECT <include refid="cols"/> FROM budget
+        WHERE member_id = #{memberId} AND `year` = #{year} AND `month` = #{month}
+        ORDER BY category
     </select>
 
     <select id="findByIdAndMember" resultMap="budgetResultMap">
@@ -32,15 +36,30 @@
     <select id="countByCategory" resultType="int">
         SELECT COUNT(*) FROM budget
         WHERE member_id = #{memberId} AND category = #{category}
+          AND `year` = #{year} AND `month` = #{month}
         <if test="excludeId != null">AND id != #{excludeId}</if>
     </select>
 
     <insert id="insert" parameterType="com.sb.web.account.domain.Budget"
             useGeneratedKeys="true" keyProperty="id">
         INSERT INTO budget (member_id, category, fixed, base_unit, base_amount,
-                            daily, weekly, monthly, yearly, created_at, updated_at)
+                            daily, weekly, monthly, yearly, `year`, `month`, created_at, updated_at)
         VALUES (#{memberId}, #{category}, #{fixed}, #{baseUnit}, #{baseAmount},
-                #{daily}, #{weekly}, #{monthly}, #{yearly}, NOW(), NOW())
+                #{daily}, #{weekly}, #{monthly}, #{yearly}, #{year}, #{month}, NOW(), NOW())
+    </insert>
+
+    <!-- 전월(또는 임의 월) 예산을 다른 월로 복사. 같은 분류는 덮어씀(ON DUPLICATE) -->
+    <insert id="copyMonth">
+        INSERT INTO budget (member_id, category, fixed, base_unit, base_amount,
+                            daily, weekly, monthly, yearly, `year`, `month`, created_at, updated_at)
+        SELECT member_id, category, fixed, base_unit, base_amount,
+               daily, weekly, monthly, yearly, #{toYear}, #{toMonth}, NOW(), NOW()
+        FROM budget
+        WHERE member_id = #{memberId} AND `year` = #{fromYear} AND `month` = #{fromMonth}
+        ON DUPLICATE KEY UPDATE
+            fixed = VALUES(fixed), base_unit = VALUES(base_unit), base_amount = VALUES(base_amount),
+            daily = VALUES(daily), weekly = VALUES(weekly), monthly = VALUES(monthly),
+            yearly = VALUES(yearly), updated_at = NOW()
     </insert>
 
     <update id="update" parameterType="com.sb.web.account.domain.Budget">