feat(account): add country to follow page

- Implemented country selection
- Fetches countries from repository
- Shows loading/error states

Author: fulleni

lib/account/view/add_country_to_follow_page.dart

@@ -0,0 +1,143 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:ht_main/account/bloc/account_bloc.dart';
+// TODO(cline): May need a specific BLoC for fetching all countries if not using an existing one.
+// For now, we'll assume direct repository access or a placeholder.
+import 'package:ht_main/l10n/l10n.dart';
+import 'package:ht_main/shared/constants/app_spacing.dart';
+import 'package:ht_main/shared/widgets/widgets.dart';
+import 'package:ht_shared/ht_shared.dart';
+import 'package:ht_data_repository/ht_data_repository.dart';
+
+/// {@template add_country_to_follow_page}
+/// A page that allows users to browse and select countries to follow.
+/// {@endtemplate}
+class AddCountryToFollowPage extends StatefulWidget {
+  /// {@macro add_country_to_follow_page}
+  const AddCountryToFollowPage({super.key});
+
+  @override
+  State<AddCountryToFollowPage> createState() => _AddCountryToFollowPageState();
+}
+
+class _AddCountryToFollowPageState extends State<AddCountryToFollowPage> {
+  List<Country> _allCountries = [];
+  bool _isLoading = true;
+  String? _errorMessage;
+
+  @override
+  void initState() {
+    super.initState();
+    _fetchCountries();
+  }
+
+  Future<void> _fetchCountries() async {
+    setState(() {
+      _isLoading = true;
+      _errorMessage = null;
+    });
+    try {
+      // Directly use the repository to fetch all countries
+      // This assumes the Country repository's readAll method without userId
+      // fetches all available countries.
+      final countryRepository = context.read<HtDataRepository<Country>>();
+      final paginatedResponse = await countryRepository.readAll();
+      setState(() {
+        _allCountries = paginatedResponse.items;
+        _isLoading = false;
+      });
+    } on HtHttpException catch (e) {
+      setState(() {
+        _isLoading = false;
+        _errorMessage = e.message;
+      });
+    } catch (e) {
+      setState(() {
+        _isLoading = false;
+        _errorMessage = context.l10n.unknownError;
+      });
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final l10n = context.l10n;
+
+    return Scaffold(
+      appBar: AppBar(
+        title: Text(l10n.addCountriesPageTitle), // New l10n key
+      ),
+      body: Builder(
+        builder: (context) {
+          if (_isLoading) {
+            return const Center(child: CircularProgressIndicator());
+          }
+          if (_errorMessage != null) {
+            return FailureStateWidget(
+              message: _errorMessage!,
+              onRetry: _fetchCountries,
+            );
+          }
+          if (_allCountries.isEmpty) {
+            return FailureStateWidget(
+              message: l10n.countryFilterEmptyHeadline, // Re-use
+            );
+          }
+
+          return BlocBuilder<AccountBloc, AccountState>(
+            builder: (context, accountState) {
+              final followedCountries =
+                  accountState.preferences?.followedCountries ?? [];
+
+              return ListView.builder(
+                padding: const EdgeInsets.all(AppSpacing.md),
+                itemCount: _allCountries.length,
+                itemBuilder: (context, index) {
+                  final country = _allCountries[index];
+                  final isFollowed =
+                      followedCountries.any((fc) => fc.id == country.id);
+
+                  return Card(
+                    margin: const EdgeInsets.only(bottom: AppSpacing.sm),
+                    child: ListTile(
+                      leading: country.flagUrl.isNotEmpty &&
+                              Uri.tryParse(country.flagUrl)?.isAbsolute == true
+                          ? SizedBox(
+                              width: 36,
+                              height: 24,
+                              child: Image.network(
+                                country.flagUrl,
+                                fit: BoxFit.cover,
+                                errorBuilder: (context, error, stackTrace) =>
+                                    const Icon(Icons.public_outlined),
+                              ),
+                            )
+                          : const Icon(Icons.public_outlined),
+                      title: Text(country.name),
+                      trailing: IconButton(
+                        icon: isFollowed
+                            ? Icon(
+                                Icons.check_circle,
+                                color: Theme.of(context).colorScheme.primary,
+                              )
+                            : const Icon(Icons.add_circle_outline),
+                        tooltip: isFollowed
+                            ? l10n.unfollowCountryTooltip(country.name)
+                            : l10n.followCountryTooltip(country.name), // New
+                        onPressed: () {
+                          context.read<AccountBloc>().add(
+                                AccountFollowCountryToggled(country: country),
+                              );
+                        },
+                      ),
+                    ),
+                  );
+                },
+              );
+            },
+          );
+        },
+      ),
+    );
+  }
+}