refactor(lang-detect): LanguageDetectEvent ID 필드를 단일 id로 통합

- LanguageDetectEvent의 contentId/commentId를 제거하고 공통 id(Long) 필드로 단순화
- LanguageDetectListener에서 targetType에 따라 id를 AudioContent/AudioContentComment/CharacterComment 조회에 사용하도록 수정
- AudioContentService, AudioContentCommentService, AudioContentDonationService, CharacterCommentService 등 이벤트 발행부를 새 시그니처(id + targetType)로 정리

src/main/kotlin/kr/co/vividnext/sodalive/content/LanguageDetectEvent.kt

@@ -26,10 +26,9 @@ enum class LanguageDetectTargetType {
 }
 
 class LanguageDetectEvent(
-    val contentId: Long? = null,
+    val id: Long,
     val query: String,
-    val targetType: LanguageDetectTargetType = LanguageDetectTargetType.CONTENT,
-    val commentId: Long? = null
+    val targetType: LanguageDetectTargetType = LanguageDetectTargetType.CONTENT
 )
 
 data class PapagoLanguageDetectResponse(
@@ -72,11 +71,7 @@ class LanguageDetectListener(
     }
 
     private fun handleContentLanguageDetect(event: LanguageDetectEvent) {
-        val contentId = event.contentId
-        if (contentId == null) {
-            log.warn("[PapagoLanguageDetect] contentId is null for CONTENT target. event={}", event)
-            return
-        }
+        val contentId = event.id
 
         val audioContent = audioContentRepository.findById(contentId).orElse(null)
         if (audioContent == null) {
@@ -109,11 +104,7 @@ class LanguageDetectListener(
     }
 
     private fun handleCommentLanguageDetect(event: LanguageDetectEvent) {
-        val commentId = event.commentId
-        if (commentId == null) {
-            log.warn("[PapagoLanguageDetect] commentId is null for COMMENT target. event={}", event)
-            return
-        }
+        val commentId = event.id
 
         val comment = audioContentCommentRepository.findById(commentId).orElse(null)
         if (comment == null) {
@@ -144,11 +135,7 @@ class LanguageDetectListener(
     }
 
     private fun handleCharacterCommentLanguageDetect(event: LanguageDetectEvent) {
-        val commentId = event.commentId
-        if (commentId == null) {
-            log.warn("[PapagoLanguageDetect] commentId is null for CHARACTER_COMMENT target. event={}", event)
-            return
-        }
+        val commentId = event.id
 
         val comment = characterCommentRepository.findById(commentId).orElse(null)
         if (comment == null) {