feat(filter): enforce saved filter limits in UI

Integrates the `ContentLimitationService` into the `HeadlinesFilterPage` to enforce limits on saving new filters.

When a user attempts to "Apply & Save" a filter, the app now checks if they have reached their limit. If the limit is met, a `ContentLimitationBottomSheet` is displayed to inform the user, and the save process is halted. This provides immediate, clear feedback and aligns the filter-saving feature with the app's overall content limitation strategy.

Author: fulleni

lib/headlines-feed/view/headlines_filter_page.dart

@@ -9,6 +9,8 @@ import 'package:flutter_news_app_mobile_client_full_source_code/headlines-feed/b
 import 'package:flutter_news_app_mobile_client_full_source_code/headlines-feed/bloc/headlines_filter_bloc.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/headlines-feed/models/headline_filter.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/headlines-feed/widgets/save_filter_dialog.dart';
+import 'package:flutter_news_app_mobile_client_full_source_code/shared/services/content_limitation_service.dart';
+import 'package:flutter_news_app_mobile_client_full_source_code/shared/widgets/content_limitation_bottom_sheet.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/l10n/app_localizations.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/l10n/l10n.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/router/routes.dart';
@@ -135,6 +137,24 @@ Future<void> _showApplyOptionsDialog(BuildContext context) async {
 /// be popped before the dialog is fully dismissed, which was causing a
 /// navigation stack error.
 Future<void> _saveAndApplyFilter(BuildContext context) async {
+  // Before showing the save dialog, check if the user is allowed to save
+  // another filter based on their subscription level and current usage.
+  final contentLimitationService = context.read<ContentLimitationService>();
+  final limitationStatus =
+      contentLimitationService.checkAction(ContentAction.saveFilter);
+
+  // If the user has reached their limit, show the limitation bottom sheet
+  // and halt the save process.
+  if (limitationStatus != LimitationStatus.allowed) {
+    await showModalBottomSheet<void>(
+      context: context,
+      builder: (context) => ContentLimitationBottomSheet(
+        status: limitationStatus,
+      ),
+    );
+    return;
+  }
+
   final filterState = context.read<HeadlinesFilterBloc>().state;
 
   // `showDialog` returns a Future that completes when the dialog is popped.