refactor(home): 추천 dedup 자료구조를 LinkedHashMap에서 Set+List로 교체

- HomeService: getRecommendContentList 추가 및 fetchData에 recommendContentList 주입
- HomeController: GET /api/home/recommend-contents 엔드포인트 추가
- 추천 로직은 랜덤 20개, 성인/타입/차단 필터 반영

src/main/kotlin/kr/co/vividnext/sodalive/api/home/GetHomeResponse.kt

@@ -27,5 +27,6 @@ data class GetHomeResponse(
     val recommendChannelList: List<RecommendChannelResponse>,
     val freeContentList: List<AudioContentMainItem>,
     val pointAvailableContentList: List<AudioContentMainItem>,
+    val recommendContentList: List<AudioContentMainItem>,
     val curationList: List<GetContentCurationResponse>
 )

src/main/kotlin/kr/co/vividnext/sodalive/api/home/HomeController.kt

@@ -63,4 +63,20 @@ class HomeController(private val service: HomeService) {
             )
         )
     }
+
+    // 추천 콘텐츠만 새로고침하기 위한 엔드포인트
+    @GetMapping("/recommend-contents")
+    fun getRecommendContents(
+        @RequestParam("isAdultContentVisible", required = false) isAdultContentVisible: Boolean? = null,
+        @RequestParam("contentType", required = false) contentType: ContentType? = null,
+        @AuthenticationPrincipal(expression = "#this == 'anonymousUser' ? null : member") member: Member?
+    ) = run {
+        ApiResponse.ok(
+            service.getRecommendContentList(
+                isAdultContentVisible = isAdultContentVisible ?: true,
+                contentType = contentType ?: ContentType.ALL,
+                member = member
+            )
+        )
+    }
 }

src/main/kotlin/kr/co/vividnext/sodalive/api/home/HomeService.kt

@@ -48,6 +48,11 @@ class HomeService(
     @Value("\${cloud.aws.cloud-front.host}")
     private val imageHost: String
 ) {
+    companion object {
+        private const val RECOMMEND_TARGET_SIZE = 20
+        private const val RECOMMEND_MAX_ATTEMPTS = 3
+    }
+
     fun fetchData(
         timezone: String,
         isAdultContentVisible: Boolean,
@@ -213,6 +218,11 @@ class HomeService(
             recommendChannelList = recommendChannelList,
             freeContentList = freeContentList,
             pointAvailableContentList = pointAvailableContentList,
+            recommendContentList = getRecommendContentList(
+                isAdultContentVisible = isAdultContentVisible,
+                contentType = contentType,
+                member = member
+            ),
             curationList = curationList
         )
     }
@@ -284,4 +294,46 @@ class HomeService(
 
         return dayToSeriesPublishedDaysOfWeek[zonedDateTime.dayOfWeek] ?: SeriesPublishedDaysOfWeek.RANDOM
     }
+
+    // 추천 콘텐츠 조회 로직은 변경 가능성을 고려하여 별도 메서드로 추출한다.
+    fun getRecommendContentList(
+        isAdultContentVisible: Boolean,
+        contentType: ContentType,
+        member: Member?
+    ): List<AudioContentMainItem> {
+        val memberId = member?.id
+        val isAdult = member?.auth != null && isAdultContentVisible
+
+        // Set + List 조합으로 중복 제거 및 순서 보존, 각 시도마다 limit=60으로 조회
+        val seen = HashSet<Long>(RECOMMEND_TARGET_SIZE * 2)
+        val result = ArrayList<AudioContentMainItem>(RECOMMEND_TARGET_SIZE)
+        var attempt = 0
+        while (attempt < RECOMMEND_MAX_ATTEMPTS && result.size < RECOMMEND_TARGET_SIZE) {
+            attempt += 1
+            val batch = contentService.getLatestContentByTheme(
+                theme = emptyList(), // 특정 테마에 종속되지 않도록 전체에서 랜덤 조회
+                contentType = contentType,
+                offset = 0,
+                limit = (RECOMMEND_TARGET_SIZE * RECOMMEND_MAX_ATTEMPTS).toLong(), // 60개 조회
+                isFree = false,
+                isAdult = isAdult,
+                orderByRandom = true
+            ).filter {
+                if (memberId != null) {
+                    !memberService.isBlocked(blockedMemberId = memberId, memberId = it.creatorId)
+                } else {
+                    true
+                }
+            }
+
+            for (item in batch) {
+                if (result.size >= RECOMMEND_TARGET_SIZE) break
+                if (seen.add(item.contentId)) {
+                    result.add(item)
+                }
+            }
+        }
+
+        return result
+    }
 }