feat(home): AI 캐릭터 부족분을 랜덤 보충한다

src/main/kotlin/kr/co/vividnext/sodalive/v2/api/home/application/HomeRecommendationFacade.kt

@@ -75,7 +75,10 @@ class HomeRecommendationFacade(
                     includeAdultContents = includeAdult
                 )
                     .map { it.toItem() },
-                aiCharacters = queryService.findAiCharacterRecommendations(limit = HOME_AI_CHARACTER_LIMIT).map { it.toItem() },
+                aiCharacters = queryService.findAiCharacterRecommendations(
+                    limit = HOME_AI_CHARACTER_LIMIT,
+                    backfillRandom = true
+                ).map { it.toItem() },
                 genreCreators = queryService.findGenreCreatorRecommendations(
                     memberId = member?.id,
                     includeAdultGenres = includeAdult,

src/main/kotlin/kr/co/vividnext/sodalive/v2/recommendation/adapter/out/persistence/DefaultHomeRecommendationQueryRepository.kt

@@ -775,6 +775,29 @@ class DefaultHomeRecommendationQueryRepository(
             .fetch()
     }
 
+    override fun findRandomAiCharacterRecommendationIds(
+        excludeCharacterIds: List<Long>,
+        limit: Int
+    ): List<Long> {
+        val creatorMember = QMember("creatorMember")
+        val randomTieBreaker = Expressions.numberTemplate(Double::class.java, "function('rand')")
+
+        return queryFactory
+            .select(chatCharacter.id)
+            .from(chatCharacter)
+            .join(chatCharacter.creatorMember, creatorMember)
+            .where(
+                chatCharacter.isActive.isTrue,
+                excludeAiCharacterCondition(excludeCharacterIds),
+                creatorMember.isActive.isTrue,
+                creatorMember.role.eq(MemberRole.CREATOR),
+                creatorMember.memberKind.eq(MemberKind.AI_CHARACTER)
+            )
+            .orderBy(randomTieBreaker.asc())
+            .limit(limit.toLong())
+            .fetch()
+    }
+
     override fun findCheerCreatorRecommendationDetails(
         creatorIds: List<Long>,
         memberId: Long?
@@ -1235,6 +1258,10 @@ class DefaultHomeRecommendationQueryRepository(
         return if (includeAdultLives) null else liveRoom.isAdult.isFalse
     }
 
+    private fun excludeAiCharacterCondition(excludeCharacterIds: List<Long>): BooleanExpression? {
+        return if (excludeCharacterIds.isEmpty()) null else chatCharacter.id.notIn(excludeCharacterIds)
+    }
+
     private fun notBlockedCreatorCondition(memberId: Long?, creatorIdPath: Expression<Long>): BooleanExpression? {
         if (memberId == null) return null
         val blockMember = QBlockMember("recommendationBlockMember")

src/main/kotlin/kr/co/vividnext/sodalive/v2/recommendation/application/HomeRecommendationQueryService.kt

@@ -78,13 +78,23 @@ class HomeRecommendationQueryService(
 
     fun findAiCharacterRecommendations(
         offset: Long = 0,
-        limit: Int = DEFAULT_AI_CHARACTER_LIMIT
+        limit: Int = DEFAULT_AI_CHARACTER_LIMIT,
+        backfillRandom: Boolean = false
     ): List<HomeAiCharacterRecommendationRecord> {
         val snapshots = findAiCharacterSnapshotsWithFallback(offset, limit)
         val detailsById = queryPort.findAiCharacterRecommendationDetails(snapshots.map { it.targetId })
             .associateBy { it.characterId }
+        val snapshotDetails = snapshots.mapNotNull { detailsById[it.targetId] }
 
-        return snapshots.mapNotNull { detailsById[it.targetId] }
+        if (!backfillRandom || snapshots.isEmpty() || snapshotDetails.size >= limit) return snapshotDetails
+
+        val randomIds = queryPort.findRandomAiCharacterRecommendationIds(
+            excludeCharacterIds = snapshots.map { it.targetId },
+            limit = limit - snapshotDetails.size
+        )
+        val randomDetailsById = queryPort.findAiCharacterRecommendationDetails(randomIds).associateBy { it.characterId }
+        val randomDetails = randomIds.mapNotNull { randomDetailsById[it] }
+        return (snapshotDetails + randomDetails).distinctBy { it.characterId }.take(limit)
     }
 
     private fun findAiCharacterSnapshotsWithFallback(

src/main/kotlin/kr/co/vividnext/sodalive/v2/recommendation/port/out/HomeRecommendationQueryPort.kt

@@ -58,6 +58,11 @@ interface HomeRecommendationQueryPort {
 
     fun findAiCharacterRecommendationDetails(characterIds: List<Long>): List<HomeAiCharacterRecommendationRecord>
 
+    fun findRandomAiCharacterRecommendationIds(
+        excludeCharacterIds: List<Long>,
+        limit: Int
+    ): List<Long>
+
     fun findCheerCreatorRecommendationDetails(
         creatorIds: List<Long>,
         memberId: Long? = null