feat(auth): 애플 로그인 API — Sign in with Apple identity token 검증(JWKS)

- POST /api/auth/apple — nimbus-jose-jwt 로 애플 공개키(JWKS) 서명 검증 + iss/aud(번들ID)/exp 확인
- member.apple_id 컬럼(멱등 ALTER) + findByAppleId/linkApple, 구글과 동일한 이메일 자동연결 로직
- app.apple-client-id 설정(기본 kr.sblog.slimbudget)

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

src/main/resources/mapper/MemberMapper.xml

@@ -12,6 +12,7 @@
         <result property="provider" column="provider"/>
         <result property="providerId" column="provider_id"/>
         <result property="googleId" column="google_id"/>
+        <result property="appleId" column="apple_id"/>
         <result property="googlePicture" column="google_picture"/>
         <result property="profileImage" column="profile_image"/>
         <result property="role" column="role"/>
@@ -26,7 +27,7 @@
     </resultMap>
 
     <sql id="columns">
-        id, login_id, password, name, email, provider, provider_id, google_id, google_picture, profile_image, role, plan, plan_expires_at, plan_product, plan_auto_renew, points, status, created_at, updated_at
+        id, login_id, password, name, email, provider, provider_id, google_id, apple_id, google_picture, profile_image, role, plan, plan_expires_at, plan_product, plan_auto_renew, points, status, created_at, updated_at
     </sql>
 
     <select id="findById" parameterType="long" resultMap="memberResultMap">
@@ -68,15 +69,34 @@
         UPDATE member SET google_id = #{googleId}, updated_at = NOW() WHERE id = #{id}
     </update>
 
+    <!-- 애플 sub 로 회원 조회 (연결된 LOCAL 계정 + 순수 애플 계정 모두 apple_id 로 찾음) -->
+    <select id="findByAppleId" parameterType="string" resultMap="memberResultMap">
+        SELECT <include refid="columns"/> FROM member WHERE apple_id = #{appleId}
+    </select>
+
+    <!-- 애플 로그인 시 같은 이메일의 기존 계정 1건(연결 대상). LOCAL 계정 우선, 애플 미연결만. -->
+    <select id="findByEmailForAppleLink" parameterType="string" resultMap="memberResultMap">
+        SELECT <include refid="columns"/>
+        FROM member
+        WHERE email = #{email} AND status = 'ACTIVE' AND apple_id IS NULL
+        ORDER BY (provider = 'LOCAL') DESC, id ASC
+        LIMIT 1
+    </select>
+
+    <!-- 기존 계정에 애플 연결 (provider 는 그대로 유지) -->
+    <update id="linkApple">
+        UPDATE member SET apple_id = #{appleId}, updated_at = NOW() WHERE id = #{id}
+    </update>
+
     <select id="countByLoginId" parameterType="string" resultType="int">
         SELECT COUNT(*) FROM member WHERE login_id = #{loginId}
     </select>
 
     <insert id="insert" parameterType="com.sb.web.auth.domain.Member"
             useGeneratedKeys="true" keyProperty="id">
-        INSERT INTO member (login_id, password, name, email, provider, provider_id, google_id, google_picture, role, status, created_at, updated_at)
+        INSERT INTO member (login_id, password, name, email, provider, provider_id, google_id, apple_id, google_picture, role, status, created_at, updated_at)
         VALUES (#{loginId}, #{password}, #{name}, #{email},
-                #{provider}, #{providerId}, #{googleId}, #{googlePicture}, #{role}, #{status}, NOW(), NOW())
+                #{provider}, #{providerId}, #{googleId}, #{appleId}, #{googlePicture}, #{role}, #{status}, NOW(), NOW())
     </insert>
 
     <update id="updatePassword">