Migrate to MyBatis with proper Controller→Service→Mapper layering

- Add MyBatis Spring Boot Starter with XML mappers and domain classes
- Create 9 mapper interfaces + XML: Restaurant, Video, Channel, Review,
  User, Stats, DaemonConfig, Search, Vector
- Create 10 domain classes with Lombok: Restaurant, VideoSummary,
  VideoDetail, VideoRestaurantLink, Channel, Review, UserInfo,
  DaemonConfig, SiteVisitStats, VectorSearchResult
- Create 7 new service classes: RestaurantService, VideoService,
  ChannelService, ReviewService, UserService, StatsService,
  DaemonConfigService
- Refactor all controllers to be thin (HTTP + auth only), delegating
  business logic to services
- Refactor SearchService, PipelineService, DaemonScheduler, AuthService,
  YouTubeService to use mappers/services instead of JDBC/repositories
- Add Jackson SNAKE_CASE property naming for consistent API responses
- Add ClobTypeHandler for Oracle CLOB→String in MyBatis
- Add IdGenerator utility for centralized UUID generation
- Delete old repository/ package (6 files), JdbcConfig, LowerCaseKeyAdvice
- VectorService retains JDBC for Oracle VECTOR type support

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

backend-java/src/main/resources/mybatis/mapper/UserMapper.xml

@@ -0,0 +1,53 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
+<mapper namespace="com.tasteby.mapper.UserMapper">
+
+    <resultMap id="userResultMap" type="com.tasteby.domain.UserInfo">
+        <id property="id" column="id"/>
+        <result property="email" column="email"/>
+        <result property="nickname" column="nickname"/>
+        <result property="avatarUrl" column="avatar_url"/>
+        <result property="isAdmin" column="is_admin" javaType="boolean"/>
+        <result property="provider" column="provider"/>
+        <result property="createdAt" column="created_at"/>
+        <result property="favoriteCount" column="favorite_count"/>
+        <result property="reviewCount" column="review_count"/>
+    </resultMap>
+
+    <select id="findByProviderAndProviderId" resultMap="userResultMap">
+        SELECT id, email, nickname, avatar_url, is_admin, provider, created_at
+        FROM tasteby_users
+        WHERE provider = #{provider} AND provider_id = #{providerId}
+    </select>
+
+    <update id="updateLastLogin">
+        UPDATE tasteby_users SET last_login_at = SYSTIMESTAMP WHERE id = #{id}
+    </update>
+
+    <insert id="insert">
+        INSERT INTO tasteby_users (id, provider, provider_id, email, nickname, avatar_url)
+        VALUES (#{id}, #{provider}, #{providerId}, #{email}, #{nickname}, #{avatarUrl})
+    </insert>
+
+    <select id="findById" resultMap="userResultMap">
+        SELECT id, email, nickname, avatar_url, is_admin, provider, created_at
+        FROM tasteby_users
+        WHERE id = #{id}
+    </select>
+
+    <select id="findAllWithCounts" resultMap="userResultMap">
+        SELECT u.id, u.email, u.nickname, u.avatar_url, u.provider, u.created_at,
+               NVL(fav.cnt, 0) AS favorite_count,
+               NVL(rev.cnt, 0) AS review_count
+        FROM tasteby_users u
+        LEFT JOIN (SELECT user_id, COUNT(*) AS cnt FROM user_favorites GROUP BY user_id) fav ON fav.user_id = u.id
+        LEFT JOIN (SELECT user_id, COUNT(*) AS cnt FROM user_reviews GROUP BY user_id) rev ON rev.user_id = u.id
+        ORDER BY u.created_at DESC
+        OFFSET #{offset} ROWS FETCH NEXT #{limit} ROWS ONLY
+    </select>
+
+    <select id="countAll" resultType="int">
+        SELECT COUNT(*) FROM tasteby_users
+    </select>
+
+</mapper>