feat(ranking): 스냅샷 완전 공백 조회를 추가한다

src/main/kotlin/kr/co/vividnext/sodalive/v2/ranking/adapter/out/persistence/DefaultCreatorRankingSnapshotRepository.kt

@@ -28,6 +28,10 @@ class DefaultCreatorRankingSnapshotRepository(
         return repository.findPreviousCompletedSnapshots().map { it.toRecord() }
     }
 
+    override fun isSnapshotTableEmpty(): Boolean {
+        return repository.count() == 0L
+    }
+
     @Transactional
     override fun replaceSnapshots(
         aggregationStartAtUtc: LocalDateTime,

src/main/kotlin/kr/co/vividnext/sodalive/v2/ranking/port/out/CreatorRankingSnapshotPort.kt

@@ -12,6 +12,8 @@ interface CreatorRankingSnapshotPort {
 
     fun findPreviousCompletedSnapshots(): List<CreatorRankingSnapshotRecord>
 
+    fun isSnapshotTableEmpty(): Boolean
+
     fun replaceSnapshots(
         aggregationStartAtUtc: LocalDateTime,
         aggregationEndAtUtc: LocalDateTime,