feat(backend): #356 영상-식당 관련도 LLM 평가

- DB V20260615b: video_restaurants.{relevance, relevance_reason, relevance_evaluated_at} + idx_vr_relevance
- VideoRelevanceService (#322 패턴): @Async verifyAsync + verify + verifyAll(batchSize)
- PipelineService.processExtract → linkVideoRestaurant 후 verifyAsync(linkId) 자동 트리거
- GET /api/restaurants/{id}/videos: 기본 strong/unknown만, ?include_weak=true 시 모두 + relevance/reason
- AdminVideoRelevanceController: GET pending / POST all / POST {id}/evaluate / PATCH {id}
- 캐시 키 strong|all 분리, LLM 실패 시 unknown 안전 기본값(표시 유지)

Refs: #356 (close)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend-java/src/main/resources/db/migration/V20260615b__video_relevance.sql

@@ -0,0 +1,7 @@
+-- #356 영상-식당 관련도 LLM 평가
+ALTER TABLE video_restaurants ADD (
+  relevance VARCHAR2(16) DEFAULT 'unknown' NOT NULL,
+  relevance_reason VARCHAR2(120),
+  relevance_evaluated_at TIMESTAMP
+);
+CREATE INDEX idx_vr_relevance ON video_restaurants(relevance);

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

@@ -69,14 +69,20 @@
     </select>
 
     <select id="findVideoLinks" resultType="map">
-        SELECT v.video_id, v.title, v.url,
+        <!-- #356 — relevance 컬럼 SELECT + includeWeak 가드 -->
+        SELECT vr.id AS link_id,
+               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,
+               vr.relevance, vr.relevance_reason,
                c.channel_name, c.channel_id
         FROM video_restaurants vr
         JOIN videos v ON v.id = vr.video_id
         JOIN channels c ON c.id = v.channel_id
         WHERE vr.restaurant_id = #{restaurantId}
+        <if test="includeWeak == null or !includeWeak">
+            AND vr.relevance IN ('strong', 'unknown')
+        </if>
         ORDER BY v.published_at DESC
     </select>
 
@@ -315,4 +321,36 @@
         SELECT COUNT(*) FROM restaurants WHERE verified_at IS NULL
     </select>
 
+    <!-- ===== #356 영상-식당 관련도 ===== -->
+
+    <update id="updateLinkRelevance">
+        UPDATE video_restaurants
+        SET relevance = #{relevance},
+            relevance_reason = #{reason,jdbcType=VARCHAR},
+            relevance_evaluated_at = CURRENT_TIMESTAMP
+        WHERE id = #{linkId}
+    </update>
+
+    <select id="findLinkContext" resultType="map">
+        <!-- LLM 평가에 필요한 정보 -->
+        SELECT vr.id AS link_id, vr.foods_mentioned, vr.evaluation,
+               r.id AS restaurant_id, r.name AS restaurant_name, r.address, r.cuisine_type,
+               v.title AS video_title, c.channel_name
+        FROM video_restaurants vr
+        JOIN restaurants r ON r.id = vr.restaurant_id
+        JOIN videos v ON v.id = vr.video_id
+        JOIN channels c ON c.id = v.channel_id
+        WHERE vr.id = #{linkId}
+    </select>
+
+    <select id="findUnevaluatedLinks" resultType="map">
+        SELECT id AS link_id FROM video_restaurants
+        WHERE relevance_evaluated_at IS NULL
+        FETCH FIRST #{limit} ROWS ONLY
+    </select>
+
+    <select id="countUnevaluatedLinks" resultType="int">
+        SELECT COUNT(*) FROM video_restaurants WHERE relevance_evaluated_at IS NULL
+    </select>
+
 </mapper>