feat(chat-character): 캐릭터 상세 페이지 API 연동 및 UI 상태 처리

- CharacterApi에 캐릭터 상세 조회 엔드포인트 추가
- CharacterDetailRepository 생성 및 Koin DI 등록
- CharacterDetailViewModel에서 실제 API 호출/로딩/에러 상태 관리
- CharacterDetailActivity에서 loadMock 제거 후 load 호출, Koin 주입으로 전환
- 로딩 다이얼로그 및 에러 토스트 처리 로직 추가

app/src/main/java/kr/co/vividnext/sodalive/di/AppDI.kt

@@ -67,6 +67,8 @@ import kr.co.vividnext.sodalive.audition.role.AuditionRoleDetailViewModel
 import kr.co.vividnext.sodalive.chat.character.CharacterApi
 import kr.co.vividnext.sodalive.chat.character.CharacterTabRepository
 import kr.co.vividnext.sodalive.chat.character.CharacterTabViewModel
+import kr.co.vividnext.sodalive.chat.character.detail.CharacterDetailRepository
+import kr.co.vividnext.sodalive.chat.character.detail.CharacterDetailViewModel
 import kr.co.vividnext.sodalive.chat.talk.TalkApi
 import kr.co.vividnext.sodalive.chat.talk.TalkTabRepository
 import kr.co.vividnext.sodalive.chat.talk.TalkTabViewModel
@@ -351,6 +353,7 @@ class AppDI(private val context: Context, isDebugMode: Boolean) {
         viewModel { PointStatusViewModel(get()) }
         viewModel { HomeViewModel(get(), get()) }
         viewModel { CharacterTabViewModel(get()) }
+        viewModel { CharacterDetailViewModel(get()) }
         viewModel { TalkTabViewModel(get()) }
     }
 
@@ -397,6 +400,7 @@ class AppDI(private val context: Context, isDebugMode: Boolean) {
         factory { PointStatusRepository(get()) }
         factory { HomeRepository(get()) }
         factory { CharacterTabRepository(get()) }
+        factory { CharacterDetailRepository(get()) }
         factory { TalkTabRepository(get()) }
     }