Fix login 401, admin permission, video links serialization, and admin UI styling

- Fix UserInfo boolean field naming (isAdmin → admin) for proper Jackson/MyBatis mapping
- Configure Google OAuth audience with actual client ID to fix token verification
- Parse CLOB fields and convert Oracle TIMESTAMP in restaurant video links API
- Add explicit bg-white/text-gray-900 to admin page inputs, selects, and table headers
- Add keyPrefix to RestaurantList to avoid duplicate React keys across desktop/mobile

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

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

@@ -60,7 +60,8 @@
     </select>
 
     <select id="findVideoLinks" resultType="map">
-        SELECT v.video_id, v.title, v.url, v.published_at,
+        SELECT v.video_id, v.title, v.url,
+               TO_CHAR(v.published_at, 'YYYY-MM-DD"T"HH24:MI:SS') AS published_at,
                vr.foods_mentioned, vr.evaluation, vr.guests,
                c.channel_name, c.channel_id
         FROM video_restaurants vr

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

@@ -7,7 +7,7 @@
         <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="admin" column="is_admin" javaType="boolean"/>
         <result property="provider" column="provider"/>
         <result property="createdAt" column="created_at"/>
         <result property="favoriteCount" column="favorite_count"/>