feat(recommend): 추천 스냅샷 저장소를 추가한다

src/main/kotlin/kr/co/vividnext/sodalive/v2/recommend/adapter/out/persistence/RecommendationSnapshot.kt

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+package kr.co.vividnext.sodalive.v2.recommend.adapter.out.persistence
+
+import kr.co.vividnext.sodalive.common.BaseEntity
+import kr.co.vividnext.sodalive.v2.recommend.domain.RecommendedSectionType
+import java.time.LocalDateTime
+import javax.persistence.Column
+import javax.persistence.Entity
+import javax.persistence.EnumType
+import javax.persistence.Enumerated
+import javax.persistence.Table
+
+@Entity
+@Table(name = "recommendation_snapshot")
+class RecommendationSnapshot(
+    @Enumerated(EnumType.STRING)
+    @Column(name = "section_type", nullable = false, updatable = false, length = 50)
+    val sectionType: RecommendedSectionType,
+
+    @Column(name = "target_id", nullable = false, updatable = false)
+    val targetId: Long,
+
+    @Column(name = "score", nullable = false, updatable = false)
+    val score: Double,
+
+    @Column(name = "snapshot_at", nullable = false, updatable = false)
+    val snapshotAt: LocalDateTime,
+
+    @Column(name = "random_tie_breaker", nullable = false, updatable = false)
+    val randomTieBreaker: Double
+) : BaseEntity()

src/main/kotlin/kr/co/vividnext/sodalive/v2/recommend/adapter/out/persistence/RecommendationSnapshotPersistenceAdapter.kt

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+package kr.co.vividnext.sodalive.v2.recommend.adapter.out.persistence
+
+import kr.co.vividnext.sodalive.v2.recommend.domain.RecommendedSectionType
+import kr.co.vividnext.sodalive.v2.recommend.port.out.RecommendationSnapshotPort
+import kr.co.vividnext.sodalive.v2.recommend.port.out.RecommendationSnapshotRecord
+import org.springframework.stereotype.Repository
+import java.time.LocalDateTime
+
+@Repository
+class RecommendationSnapshotPersistenceAdapter(
+    private val repository: RecommendationSnapshotRepository
+) : RecommendationSnapshotPort {
+    override fun findLatestSnapshots(sectionType: RecommendedSectionType): List<RecommendationSnapshotRecord> {
+        val snapshotAt = repository.findTopBySectionTypeOrderBySnapshotAtDesc(sectionType)?.snapshotAt ?: return emptyList()
+        return repository.findAllBySectionTypeAndSnapshotAtOrderByScoreDescRandomTieBreakerAsc(sectionType, snapshotAt)
+            .map { it.toRecord() }
+    }
+
+    override fun replaceSnapshots(
+        sectionType: RecommendedSectionType,
+        snapshotAt: LocalDateTime,
+        newSnapshots: List<RecommendationSnapshotRecord>
+    ) {
+        repository.deleteBySectionTypeAndSnapshotAt(sectionType, snapshotAt)
+        repository.saveAll(newSnapshots.map { it.toEntity() })
+    }
+
+    private fun RecommendationSnapshot.toRecord(): RecommendationSnapshotRecord {
+        return RecommendationSnapshotRecord(
+            sectionType = sectionType,
+            targetId = targetId,
+            score = score,
+            snapshotAt = snapshotAt,
+            randomTieBreaker = randomTieBreaker
+        )
+    }
+
+    private fun RecommendationSnapshotRecord.toEntity(): RecommendationSnapshot {
+        return RecommendationSnapshot(
+            sectionType = sectionType,
+            targetId = targetId,
+            score = score,
+            snapshotAt = snapshotAt,
+            randomTieBreaker = randomTieBreaker
+        )
+    }
+}

src/main/kotlin/kr/co/vividnext/sodalive/v2/recommend/adapter/out/persistence/RecommendationSnapshotRepository.kt

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+package kr.co.vividnext.sodalive.v2.recommend.adapter.out.persistence
+
+import kr.co.vividnext.sodalive.v2.recommend.domain.RecommendedSectionType
+import org.springframework.data.jpa.repository.JpaRepository
+import java.time.LocalDateTime
+
+interface RecommendationSnapshotRepository : JpaRepository<RecommendationSnapshot, Long> {
+    fun findTopBySectionTypeOrderBySnapshotAtDesc(sectionType: RecommendedSectionType): RecommendationSnapshot?
+
+    fun findAllBySectionTypeAndSnapshotAtOrderByScoreDescRandomTieBreakerAsc(
+        sectionType: RecommendedSectionType,
+        snapshotAt: LocalDateTime
+    ): List<RecommendationSnapshot>
+
+    fun deleteBySectionTypeAndSnapshotAt(sectionType: RecommendedSectionType, snapshotAt: LocalDateTime)
+}

src/main/kotlin/kr/co/vividnext/sodalive/v2/recommend/port/out/RecommendationSnapshotPort.kt

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+package kr.co.vividnext.sodalive.v2.recommend.port.out
+
+import kr.co.vividnext.sodalive.v2.recommend.domain.RecommendedSectionType
+import java.time.LocalDateTime
+
+interface RecommendationSnapshotPort {
+    fun findLatestSnapshots(sectionType: RecommendedSectionType): List<RecommendationSnapshotRecord>
+
+    fun replaceSnapshots(
+        sectionType: RecommendedSectionType,
+        snapshotAt: LocalDateTime,
+        newSnapshots: List<RecommendationSnapshotRecord>
+    )
+}
+
+data class RecommendationSnapshotRecord(
+    val sectionType: RecommendedSectionType,
+    val targetId: Long,
+    val score: Double,
+    val snapshotAt: LocalDateTime,
+    val randomTieBreaker: Double
+)

src/test/kotlin/kr/co/vividnext/sodalive/v2/recommend/adapter/out/persistence/RecommendationSnapshotPersistenceAdapterTest.kt

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+package kr.co.vividnext.sodalive.v2.recommend.adapter.out.persistence
+
+import kr.co.vividnext.sodalive.configs.QueryDslConfig
+import kr.co.vividnext.sodalive.v2.recommend.domain.RecommendedSectionType
+import kr.co.vividnext.sodalive.v2.recommend.port.out.RecommendationSnapshotRecord
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+import org.springframework.beans.factory.annotation.Autowired
+import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest
+import org.springframework.context.annotation.Import
+import java.time.LocalDateTime
+
+@DataJpaTest(
+    properties = [
+        "spring.cache.type=none",
+        "spring.datasource.url=jdbc:h2:mem:testdb;MODE=MySQL;NON_KEYWORDS=VALUE"
+    ]
+)
+@Import(QueryDslConfig::class)
+class RecommendationSnapshotPersistenceAdapterTest @Autowired constructor(
+    private val repository: RecommendationSnapshotRepository
+) {
+    private val adapter = RecommendationSnapshotPersistenceAdapter(repository)
+
+    @Test
+    fun shouldFindLatestSnapshotsByLatestSnapshotAtAndScoreDescendingTieBreakerAscending() {
+        val oldSnapshotAt = LocalDateTime.of(2026, 5, 28, 23, 59, 59)
+        val latestSnapshotAt = LocalDateTime.of(2026, 5, 29, 23, 59, 59)
+        repository.saveAll(
+            listOf(
+                snapshot(RecommendedSectionType.AI_CHARACTER, targetId = 1L, score = 999.0, snapshotAt = oldSnapshotAt),
+                snapshot(
+                    RecommendedSectionType.AI_CHARACTER,
+                    targetId = 2L,
+                    score = 100.0,
+                    snapshotAt = latestSnapshotAt,
+                    randomTieBreaker = 0.9
+                ),
+                snapshot(
+                    RecommendedSectionType.AI_CHARACTER,
+                    targetId = 3L,
+                    score = 200.0,
+                    snapshotAt = latestSnapshotAt,
+                    randomTieBreaker = 0.8
+                ),
+                snapshot(
+                    RecommendedSectionType.AI_CHARACTER,
+                    targetId = 4L,
+                    score = 100.0,
+                    snapshotAt = latestSnapshotAt,
+                    randomTieBreaker = 0.1
+                ),
+                snapshot(RecommendedSectionType.CHEER_CREATOR, targetId = 5L, score = 300.0, snapshotAt = latestSnapshotAt)
+            )
+        )
+
+        val latestSnapshots = adapter.findLatestSnapshots(RecommendedSectionType.AI_CHARACTER)
+
+        assertEquals(listOf(3L, 4L, 2L), latestSnapshots.map { it.targetId })
+        assertEquals(listOf(latestSnapshotAt, latestSnapshotAt, latestSnapshotAt), latestSnapshots.map { it.snapshotAt })
+    }
+
+    @Test
+    fun shouldReplaceSnapshotsByDeletingSameSectionSnapshotAtOnly() {
+        val oldSnapshotAt = LocalDateTime.of(2026, 5, 28, 23, 59, 59)
+        val snapshotAt = LocalDateTime.of(2026, 5, 29, 23, 59, 59)
+        repository.saveAll(
+            listOf(
+                snapshot(RecommendedSectionType.AI_CHARACTER, targetId = 1L, score = 100.0, snapshotAt = oldSnapshotAt),
+                snapshot(RecommendedSectionType.AI_CHARACTER, targetId = 2L, score = 200.0, snapshotAt = snapshotAt),
+                snapshot(RecommendedSectionType.CHEER_CREATOR, targetId = 3L, score = 300.0, snapshotAt = snapshotAt)
+            )
+        )
+
+        adapter.replaceSnapshots(
+            RecommendedSectionType.AI_CHARACTER,
+            snapshotAt,
+            listOf(
+                RecommendationSnapshotRecord(
+                    sectionType = RecommendedSectionType.AI_CHARACTER,
+                    targetId = 4L,
+                    score = 400.0,
+                    snapshotAt = snapshotAt,
+                    randomTieBreaker = 0.4
+                )
+            )
+        )
+
+        assertEquals(listOf(4L), adapter.findLatestSnapshots(RecommendedSectionType.AI_CHARACTER).map { it.targetId })
+        assertEquals(listOf(3L), adapter.findLatestSnapshots(RecommendedSectionType.CHEER_CREATOR).map { it.targetId })
+        assertEquals(3, repository.findAll().size)
+    }
+
+    private fun snapshot(
+        sectionType: RecommendedSectionType,
+        targetId: Long,
+        score: Double,
+        snapshotAt: LocalDateTime,
+        randomTieBreaker: Double = 0.1
+    ): RecommendationSnapshot {
+        return RecommendationSnapshot(
+            sectionType = sectionType,
+            targetId = targetId,
+            score = score,
+            snapshotAt = snapshotAt,
+            randomTieBreaker = randomTieBreaker
+        )
+    }
+}