feat(account): add followed countries list page

- Implement FollowedCountriesListPage widget to display and manage followed countries
- Add functionality to load, display, and interact with followed countries
- Include error handling and loading states
- Enable navigation to add new countries and view country details

Author: fulleni

lib/account/view/manage_followed_items/countries/followed_countries_list_page.dart

@@ -0,0 +1,112 @@
+import 'package:core/core.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:flutter_news_app_mobile_client_full_source_code/account/bloc/account_bloc.dart';
+import 'package:flutter_news_app_mobile_client_full_source_code/entity_details/view/entity_details_page.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:go_router/go_router.dart';
+import 'package:ui_kit/ui_kit.dart';
+
+/// {@template followed_countries_list_page}
+/// Page to display and manage countries followed by the user.
+/// {@endtemplate}
+class FollowedCountriesListPage extends StatelessWidget {
+  /// {@macro followed_countries_list_page}
+  const FollowedCountriesListPage({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    final l10n = AppLocalizationsX(context).l10n;
+    final followedCountries =
+        context.watch<AccountBloc>().state.preferences?.followedCountries ?? [];
+
+    return Scaffold(
+      appBar: AppBar(
+        title: Text(l10n.followedCountriesPageTitle),
+        actions: [
+          IconButton(
+            icon: const Icon(Icons.add_circle_outline),
+            tooltip: l10n.addCountriesTooltip,
+            onPressed: () {
+              context.goNamed(Routes.addCountryToFollowName);
+            },
+          ),
+        ],
+      ),
+      body: BlocBuilder<AccountBloc, AccountState>(
+        builder: (context, state) {
+          if (state.status == AccountStatus.loading &&
+              state.preferences == null) {
+            return LoadingStateWidget(
+              icon: Icons.flag_outlined,
+              headline: l10n.followedCountriesLoadingHeadline,
+              subheadline: l10n.pleaseWait,
+            );
+          }
+
+          if (state.status == AccountStatus.failure &&
+              state.preferences == null) {
+            return FailureStateWidget(
+              exception:
+                  state.error ??
+                  OperationFailedException(l10n.followedCountriesErrorHeadline),
+              onRetry: () {
+                if (state.user?.id != null) {
+                  context.read<AccountBloc>().add(
+                    AccountLoadUserPreferences(userId: state.user!.id),
+                  );
+                }
+              },
+            );
+          }
+
+          if (followedCountries.isEmpty) {
+            return InitialStateWidget(
+              icon: Icons.public_off_outlined,
+              headline: l10n.followedCountriesEmptyHeadline,
+              subheadline: l10n.followedCountriesEmptySubheadline,
+            );
+          }
+
+          return ListView.builder(
+            itemCount: followedCountries.length,
+            itemBuilder: (context, index) {
+              final country = followedCountries[index];
+              return ListTile(
+                leading: SizedBox(
+                  width: 40,
+                  height: 40,
+                  child: Image.network(
+                    country.flagUrl,
+                    errorBuilder: (context, error, stackTrace) =>
+                        const Icon(Icons.flag_outlined),
+                  ),
+                ),
+                title: Text(country.name),
+                trailing: IconButton(
+                  icon: const Icon(
+                    Icons.remove_circle_outline,
+                    color: Colors.red,
+                  ),
+                  tooltip: l10n.unfollowCountryTooltip(country.name),
+                  onPressed: () {
+                    context.read<AccountBloc>().add(
+                      AccountFollowCountryToggled(country: country),
+                    );
+                  },
+                ),
+                onTap: () {
+                  context.push(
+                    Routes.countryDetails,
+                    extra: EntityDetailsPageArguments(entity: country),
+                  );
+                },
+              );
+            },
+          );
+        },
+      ),
+    );
+  }
+}