refactor(dashboard): migrate to ht_ui_kit and remove app_theme import

- Replace app_spacing import with ht_ui_kit in app_shell.dart
- Remove app_theme import from app.dart
- Update AppShell build method to use AppLocalizationsX for l10n

Author: fulleni

lib/app/view/app.dart

@@ -15,7 +15,6 @@ import 'package:ht_dashboard/dashboard/bloc/dashboard_bloc.dart';
 import 'package:ht_dashboard/l10n/app_localizations.dart';
 import 'package:ht_dashboard/router/router.dart';
 // Import for app_theme.dart
-import 'package:ht_dashboard/shared/theme/app_theme.dart';
 import 'package:ht_data_repository/ht_data_repository.dart';
 import 'package:ht_kv_storage_service/ht_kv_storage_service.dart';
 import 'package:ht_shared/ht_shared.dart' hide AppStatus;

lib/app/view/app_shell.dart

@@ -5,7 +5,7 @@ import 'package:go_router/go_router.dart';
 import 'package:ht_dashboard/app/bloc/app_bloc.dart';
 import 'package:ht_dashboard/l10n/l10n.dart';
 import 'package:ht_dashboard/router/routes.dart';
-import 'package:ht_dashboard/shared/constants/app_spacing.dart';
+import 'package:ht_ui_kit/ht_ui_kit.dart';
 
 /// A responsive scaffold shell for the main application sections.
 ///
@@ -24,7 +24,7 @@ class AppShell extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final l10n = context.l10n;
+    final l10n = AppLocalizationsX(context).l10n;
     return Scaffold(
       appBar: AppBar(
         title: Text(l10n.dashboard),