feat: 멤버십(무료/유료) 게이팅 — 백엔드

- member.plan(FREE/PREMIUM) 컬럼 추가 + SessionUser/MemberResponse 노출
- auth_session 백업에 plan 저장(세션 복원 시 유료 상태 유지)
- 관리자 회원 plan 변경 API (PUT /api/admin/members/{id}/plan)
- PremiumInterceptor 로 유료 전용 경로 차단(통계/예산/고정지출/태그/OCR/투자/카드알림/백업)
  · 관리자는 플랜과 무관하게 허용, 무료 회원은 403 PREMIUM_REQUIRED
- WebConfigTest: 유료 경로 등록 회귀 가드 추가

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

src/main/resources/db/member.sql

@@ -27,6 +27,9 @@ ALTER TABLE member ADD UNIQUE KEY IF NOT EXISTS uk_member_google_id (google_id);
 -- 기존 구글 계정(provider=GOOGLE)의 sub 를 google_id 로 백필(멱등 — 이미 채워졌으면 아무 것도 안 함).
 UPDATE member SET google_id = provider_id WHERE provider = 'GOOGLE' AND google_id IS NULL AND provider_id IS NOT NULL;
 
+-- 멤버십 플랜 (무료/유료). 기존 회원은 FREE 로 시작 (멱등).
+ALTER TABLE member ADD COLUMN IF NOT EXISTS plan VARCHAR(20) NOT NULL DEFAULT 'FREE' COMMENT 'FREE / PREMIUM' AFTER role;
+
 -- ============================================================
 -- 앱 전역 설정 (단일 행, id=1). 관리자 화면에서 변경.
 -- ============================================================
@@ -47,6 +50,7 @@ CREATE TABLE IF NOT EXISTS auth_session (
     login_id    VARCHAR(50)  NULL,
     name        VARCHAR(100) NULL,
     role        VARCHAR(20)  NULL,
+    plan        VARCHAR(20)  NULL,
     provider    VARCHAR(20)  NULL,
     remember_me TINYINT(1)   NOT NULL DEFAULT 0,
     expires_at  DATETIME     NOT NULL,
@@ -54,3 +58,5 @@ CREATE TABLE IF NOT EXISTS auth_session (
     PRIMARY KEY (token),
     KEY idx_auth_session_expires (expires_at)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
+-- 멤버십 플랜 백업 (기존 세션 테이블에도 멱등 추가).
+ALTER TABLE auth_session ADD COLUMN IF NOT EXISTS plan VARCHAR(20) NULL AFTER role;

src/main/resources/mapper/AuthSessionMapper.xml

@@ -5,16 +5,16 @@
 
     <insert id="insert" parameterType="com.sb.web.auth.domain.AuthSession">
         INSERT INTO auth_session
-            (token, member_id, login_id, name, role, provider, remember_me, expires_at, created_at)
+            (token, member_id, login_id, name, role, plan, provider, remember_me, expires_at, created_at)
         VALUES
-            (#{token}, #{memberId}, #{loginId}, #{name}, #{role}, #{provider},
+            (#{token}, #{memberId}, #{loginId}, #{name}, #{role}, #{plan}, #{provider},
              #{rememberMe}, #{expiresAt}, NOW())
         ON DUPLICATE KEY UPDATE
             expires_at = #{expiresAt}
     </insert>
 
     <select id="findByToken" resultType="com.sb.web.auth.domain.AuthSession">
-        SELECT token, member_id, login_id, name, role, provider, remember_me, expires_at, created_at
+        SELECT token, member_id, login_id, name, role, plan, provider, remember_me, expires_at, created_at
         FROM auth_session
         WHERE token = #{token}
     </select>

src/main/resources/mapper/MemberMapper.xml

@@ -13,13 +13,14 @@
         <result property="providerId" column="provider_id"/>
         <result property="googleId" column="google_id"/>
         <result property="role" column="role"/>
+        <result property="plan" column="plan"/>
         <result property="status" column="status"/>
         <result property="createdAt" column="created_at"/>
         <result property="updatedAt" column="updated_at"/>
     </resultMap>
 
     <sql id="columns">
-        id, login_id, password, name, email, provider, provider_id, google_id, role, status, created_at, updated_at
+        id, login_id, password, name, email, provider, provider_id, google_id, role, plan, status, created_at, updated_at
     </sql>
 
     <select id="findById" parameterType="long" resultMap="memberResultMap">
@@ -82,6 +83,10 @@
         UPDATE member SET role = #{role}, updated_at = NOW() WHERE id = #{id}
     </update>
 
+    <update id="updatePlan">
+        UPDATE member SET plan = #{plan}, updated_at = NOW() WHERE id = #{id}
+    </update>
+
     <update id="updateStatus">
         UPDATE member SET status = #{status}, updated_at = NOW() WHERE id = #{id}
     </update>