feat(ui): add update required page

- Implement UpdateRequiredPage widget for mandatory app updates
- Add logic to launch app store URL for update
- Display error message if update URL is unavailable
- Use AppBloc to fetch remote config for platform-specific update URLs
- Reuse InitialStateWidget for consistent UI

Author: fulleni

lib/status/view/update_required_page.dart

@@ -0,0 +1,88 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:flutter_news_app_mobile_client_full_source_code/app/bloc/app_bloc.dart';
+import 'package:flutter_news_app_mobile_client_full_source_code/l10n/app_localizations.dart';
+import 'package:ui_kit/ui_kit.dart';
+import 'package:url_launcher/url_launcher.dart';
+
+/// A page displayed to the user when a mandatory app update is required.
+///
+/// This page informs the user that they must update the application to the
+/// latest version to continue using it. It provides a button that links
+/// directly to the appropriate app store page by fetching the URL from the
+/// remote configuration.
+class UpdateRequiredPage extends StatelessWidget {
+  /// {@macro update_required_page}
+  const UpdateRequiredPage({super.key});
+
+  /// Attempts to launch the given URL in an external application (e.g., browser
+  /// or app store).
+  ///
+  /// Shows a [SnackBar] with an error message if the URL cannot be launched.
+  Future<void> _launchUrl(BuildContext context, String url) async {
+    // Ensure the URL is not empty before attempting to parse.
+    if (url.isEmpty) {
+      ScaffoldMessenger.of(context)
+        ..hideCurrentSnackBar()
+        ..showSnackBar(
+          // TODO(fulleni): localize later.
+          const SnackBar(content: Text('Update URL is not available.')),
+        );
+      return;
+    }
+
+    final uri = Uri.parse(url);
+    if (await canLaunchUrl(uri)) {
+      // Launch the URL externally. This will open the App Store, Play Store,
+      // or a browser.
+      await launchUrl(uri, mode: LaunchMode.externalApplication);
+    } else {
+      // If the URL can't be launched, inform the user.
+      ScaffoldMessenger.of(context)
+        ..hideCurrentSnackBar()
+        ..showSnackBar(
+          SnackBar(content: Text('Could not open update URL: $url')),
+        );
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final l10n = AppLocalizations.of(context);
+
+    // This is the robust, production-ready way to get the update URL.
+    // It uses BlocProvider.of(context) to access the AppBloc instance and
+    // determines the correct URL based on the current platform (iOS/Android).
+    // It falls back to an empty string if the remote config is not available.
+    final appBloc = BlocProvider.of<AppBloc>(context);
+    final updateUrl = Theme.of(context).platform == TargetPlatform.android
+        ? appBloc.state.remoteConfig?.appStatus.androidUpdateUrl
+        : appBloc.state.remoteConfig?.appStatus.iosUpdateUrl;
+
+    return Scaffold(
+      body: Padding(
+        padding: const EdgeInsets.all(AppSpacing.lg),
+        child: Column(
+          mainAxisAlignment: MainAxisAlignment.center,
+          children: [
+            // Reusing the InitialStateWidget for a consistent UI.
+            InitialStateWidget(
+              icon: Icons.system_update_alt,
+              headline: l10n.updateRequiredHeadline,
+              subheadline: l10n.updateRequiredSubheadline,
+            ),
+            const SizedBox(height: AppSpacing.lg),
+            // The button to direct the user to the app store.
+            // It's disabled if the update URL is not available.
+            ElevatedButton(
+              onPressed: updateUrl != null && updateUrl.isNotEmpty
+                  ? () => _launchUrl(context, updateUrl)
+                  : null,
+              child: Text(l10n.updateRequiredButton),
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+}