fix(chat): ChatCharacter 엔티티의 isActive 속성 참조 오류 수정

src/main/kotlin/kr/co/vividnext/sodalive/admin/chat/character/service/AdminChatCharacterService.kt

@@ -22,7 +22,7 @@ class AdminChatCharacterService(
     @Transactional(readOnly = true)
     fun getActiveChatCharacters(pageable: Pageable, imageHost: String = ""): ChatCharacterListPageResponse {
         // isActive가 true인 캐릭터만 조회
-        val page = chatCharacterRepository.findByIsActiveTrue(pageable)
+        val page = chatCharacterRepository.findByActiveTrue(pageable)
 
         // 페이지 정보 생성
         val content = page.content.map { ChatCharacterListResponse.from(it, imageHost) }