add auth register

lib/features/auth/presentation/providers/cities_provider.dart

@@ -0,0 +1,62 @@
+/// Cities Provider
+///
+/// Manages the list of cities/provinces for address selection
+library;
+
+import 'package:riverpod_annotation/riverpod_annotation.dart';
+import 'package:worker/features/auth/data/datasources/auth_remote_datasource.dart';
+import 'package:worker/features/auth/domain/entities/city.dart';
+import 'package:worker/features/auth/presentation/providers/session_provider.dart';
+
+part 'cities_provider.g.dart';
+
+/// Cities Provider
+///
+/// Fetches list of cities from API for registration form.
+/// Requires active session (CSRF token and SID).
+/// keepAlive: true ensures the cities list persists and doesn't auto-dispose.
+@Riverpod(keepAlive: true)
+class Cities extends _$Cities {
+  @override
+  Future<List<City>> build() async {
+    // Don't auto-fetch on build, wait for manual call
+    return [];
+  }
+
+  /// Fetch cities from API
+  Future<void> fetchCities() async {
+    state = const AsyncValue.loading();
+
+    state = await AsyncValue.guard(() async {
+      final sessionState = ref.read(sessionProvider);
+
+      if (!sessionState.hasSession) {
+        throw Exception('No active session. Please get session first.');
+      }
+
+      final dataSource = ref.read(authRemoteDataSourceProvider);
+      return await dataSource.getCities(
+        csrfToken: sessionState.csrfToken!,
+        sid: sessionState.sid!,
+      );
+    });
+  }
+
+  /// Refresh cities list
+  Future<void> refresh() async {
+    await fetchCities();
+  }
+}
+
+/// Provider to get a specific city by code
+@riverpod
+City? cityByCode(Ref ref, String code) {
+  final citiesAsync = ref.watch(citiesProvider);
+
+  return citiesAsync.whenOrNull(
+    data: (List<City> cities) => cities.firstWhere(
+      (City city) => city.code == code,
+      orElse: () => cities.first,
+    ),
+  );
+}