chore: 불필요한 코드 및 빈 디렉토리 제거

- 미사용 파일 삭제: confirmation_dialog.dart
- 빈 디렉토리 삭제: shadcn, mappers, common/dialogs
- app_lock_provider: BuildContext async gap 경고 수정

lib/providers/app_lock_provider.dart

@@ -67,6 +67,12 @@ class AppLockProvider extends ChangeNotifier {
     }
 
     try {
+      // async 전에 context 기반 데이터 미리 획득
+      final ctx = navigatorKey.currentContext;
+      final loc = ctx != null ? AppLocalizations.of(ctx) : null;
+      final localizedReason =
+          loc?.unlockWithBiometric ?? 'Unlock with biometric authentication.';
+
       final canCheck = await _checkBiometrics();
       if (!canCheck) {
         _isLocked = false;
@@ -74,11 +80,8 @@ class AppLockProvider extends ChangeNotifier {
         return true;
       }
 
-      final ctx = navigatorKey.currentContext;
-      final loc = ctx != null ? AppLocalizations.of(ctx) : null;
       final authenticated = await _localAuth.authenticate(
-        localizedReason:
-            loc?.unlockWithBiometric ?? 'Unlock with biometric authentication.',
+        localizedReason: localizedReason,
         options: const AuthenticationOptions(
           stickyAuth: true,
           biometricOnly: true,