feat(repo): 최근 3일 내 이미지 보유 캐릭터 id 일괄 조회 쿼리 추가

- 내용: `findCharacterIdsWithRecentImages(characterIds, since)` 추가
- 본문: 왜(이유) – N+1 제거, 무엇 – IN 기반 벌크 조회

src/main/kotlin/kr/co/vividnext/sodalive/chat/character/image/CharacterImageRepository.kt

@@ -8,7 +8,9 @@ import org.springframework.data.domain.Page
 import org.springframework.data.domain.Pageable
 import org.springframework.data.jpa.repository.JpaRepository
 import org.springframework.data.jpa.repository.Query
+import org.springframework.data.repository.query.Param
 import org.springframework.stereotype.Repository
+import java.time.LocalDateTime
 
 @Repository
 interface CharacterImageRepository : JpaRepository<CharacterImage, Long>, CharacterImageQueryRepository {
@@ -26,6 +28,21 @@ interface CharacterImageRepository : JpaRepository<CharacterImage, Long>, Charac
             "WHERE ci.chatCharacter.id = :characterId AND ci.isActive = true"
     )
     fun findMaxSortOrderByCharacterId(characterId: Long): Int
+
+    @Query(
+        """
+    select distinct c.id
+    from CharacterImage ci
+    join ci.chatCharacter c
+    where ci.isActive = true
+      and ci.createdAt >= :since
+      and c.id in :characterIds
+    """
+    )
+    fun findCharacterIdsWithRecentImages(
+        @Param("characterIds") characterIds: List<Long>,
+        @Param("since") since: LocalDateTime
+    ): List<Long>
 }
 
 interface CharacterImageQueryRepository {