feat(shared): add content limitation bottom sheet

- Implement ContentLimitationBottomSheet widget to handle different user limitation statuses
- Add private widgets for anonymous, standard, and premium user limit views
- Include navigation to account linking and manage followed items pages
- Implement localization placeholders for titles, bodies, and buttons
- Create _BaseLimitView for shared layout among different limit views

Author: fulleni

lib/shared/widgets/content_limitation_bottom_sheet.dart

@@ -0,0 +1,173 @@
+import 'package:flutter/material.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';
+import 'package:flutter_news_app_mobile_client_full_source_code/shared/services/content_limitation_service.dart';
+import 'package:go_router/go_router.dart';
+import 'package:ui_kit/ui_kit.dart';
+
+/// {@template content_limitation_bottom_sheet}
+/// A bottom sheet that informs the user about content limitations and provides
+/// relevant actions based on their status.
+/// {@endtemplate}
+class ContentLimitationBottomSheet extends StatelessWidget {
+  /// {@macro content_limitation_bottom_sheet}
+  const ContentLimitationBottomSheet({required this.status, super.key});
+
+  /// The limitation status that determines the content of the bottom sheet.
+  final LimitationStatus status;
+
+  @override
+  Widget build(BuildContext context) {
+    // Use a switch to build the appropriate view based on the status.
+    // Each case returns a dedicated private widget for clarity.
+    switch (status) {
+      case LimitationStatus.anonymousLimitReached:
+        return const _AnonymousLimitView();
+      case LimitationStatus.standardUserLimitReached:
+        return const _StandardUserLimitView();
+      case LimitationStatus.premiumUserLimitReached:
+        return const _PremiumUserLimitView();
+      case LimitationStatus.allowed:
+        // If the action is allowed, no UI is needed.
+        return const SizedBox.shrink();
+    }
+  }
+}
+
+/// A private widget to show when an anonymous user hits a limit.
+class _AnonymousLimitView extends StatelessWidget {
+  const _AnonymousLimitView();
+
+  @override
+  Widget build(BuildContext context) {
+    final l10n = context.l10n;
+    final theme = Theme.of(context);
+
+    return _BaseLimitView(
+      icon: Icons.person_add_alt_1_outlined,
+      // TODO(fulleni): Add l10n.anonymousLimitTitle
+      title: 'Sign in to Save More',
+      // TODO(fulleni): Add l10n.anonymousLimitBody
+      body:
+          'Create a free account to save and follow unlimited topics, sources, and countries.',
+      child: ElevatedButton(
+        onPressed: () {
+          // Pop the bottom sheet first.
+          Navigator.of(context).pop();
+          // Then navigate to the account linking page.
+          context.pushNamed(Routes.accountLinkingName);
+        },
+        style: ElevatedButton.styleFrom(
+          minimumSize: const Size.fromHeight(AppSpacing.xxl + AppSpacing.sm),
+        ),
+        // TODO(fulleni): Add l10n.anonymousLimitButton
+        child: const Text('Sign In & Link Account'),
+      ),
+    );
+  }
+}
+
+/// A private widget to show when a standard (free) user hits a limit.
+class _StandardUserLimitView extends StatelessWidget {
+  const _StandardUserLimitView();
+
+  @override
+  Widget build(BuildContext context) {
+    final l10n = context.l10n;
+    final theme = Theme.of(context);
+
+    return _BaseLimitView(
+      icon: Icons.workspace_premium_outlined,
+      // TODO(fulleni): Add l10n.standardLimitTitle
+      title: 'Unlock Unlimited Access',
+      // TODO(fulleni): Add l10n.standardLimitBody
+      body:
+          "You've reached your limit for the free plan. Upgrade to save and follow more.",
+      child: ElevatedButton(
+        // TODO(fulleni): Implement account upgrade flow.
+        // The upgrade flow is not yet implemented, so the button is disabled.
+        onPressed: null,
+        style: ElevatedButton.styleFrom(
+          minimumSize: const Size.fromHeight(AppSpacing.xxl + AppSpacing.sm),
+        ),
+        // TODO(fulleni): Add l10n.standardLimitButton
+        child: const Text('Upgrade to Premium'),
+      ),
+    );
+  }
+}
+
+/// A private widget to show when a premium user hits a limit.
+class _PremiumUserLimitView extends StatelessWidget {
+  const _PremiumUserLimitView();
+
+  @override
+  Widget build(BuildContext context) {
+    final l10n = context.l10n;
+    final theme = Theme.of(context);
+
+    return _BaseLimitView(
+      icon: Icons.inventory_2_outlined,
+      // TODO(fulleni): Add l10n.premiumLimitTitle
+      title: "You've Reached the Limit",
+      // TODO(fulleni): Add l10n.premiumLimitBody
+      body:
+          'To add new items, please review and manage your existing saved and followed content.',
+      child: ElevatedButton(
+        onPressed: () {
+          // Pop the bottom sheet first.
+          Navigator.of(context).pop();
+          // Then navigate to the page for managing followed items.
+          context.goNamed(Routes.manageFollowedItemsName);
+        },
+        style: ElevatedButton.styleFrom(
+          minimumSize: const Size.fromHeight(AppSpacing.xxl + AppSpacing.sm),
+        ),
+        // TODO(fulleni): Add l10n.premiumLimitButton
+        child: const Text('Manage My Content'),
+      ),
+    );
+  }
+}
+
+/// A base layout for the content limitation views to reduce duplication.
+class _BaseLimitView extends StatelessWidget {
+  const _BaseLimitView({
+    required this.icon,
+    required this.title,
+    required this.body,
+    required this.child,
+  });
+
+  final IconData icon;
+  final String title;
+  final String body;
+  final Widget child;
+
+  @override
+  Widget build(BuildContext context) {
+    return Padding(
+      padding: const EdgeInsets.all(AppSpacing.paddingLarge),
+      child: Column(
+        mainAxisSize: MainAxisSize.min,
+        children: [
+          Icon(icon, size: AppSpacing.xxl * 1.5, color: Colors.blue),
+          const SizedBox(height: AppSpacing.lg),
+          Text(
+            title,
+            style: const TextStyle(fontSize: 22),
+            textAlign: TextAlign.center,
+          ),
+          const SizedBox(height: AppSpacing.md),
+          Text(
+            body,
+            style: const TextStyle(fontSize: 16),
+            textAlign: TextAlign.center,
+          ),
+          const SizedBox(height: AppSpacing.lg),
+          child,
+        ],
+      ),
+    );
+  }
+}