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/StatsMapper.xml

@@ -0,0 +1,24 @@
+<?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.StatsMapper">
+
+    <update id="recordVisit">
+        MERGE INTO site_visits sv
+        USING (SELECT TRUNC(SYSDATE) AS d FROM dual) src
+        ON (sv.visit_date = src.d)
+        WHEN MATCHED THEN UPDATE SET sv.visit_count = sv.visit_count + 1
+        WHEN NOT MATCHED THEN INSERT (visit_date, visit_count) VALUES (src.d, 1)
+    </update>
+
+    <select id="getTodayVisits" resultType="int">
+        SELECT NVL(visit_count, 0)
+        FROM site_visits
+        WHERE visit_date = TRUNC(SYSDATE)
+    </select>
+
+    <select id="getTotalVisits" resultType="int">
+        SELECT NVL(SUM(visit_count), 0)
+        FROM site_visits
+    </select>
+
+</mapper>