fix(#79): Supprimer toutes les références obsolètes à Nanny

Corrections suite au merge master:
- Suppression imports nanny_register_step*.dart (fichiers supprimés)
- Suppression variable nannyRegistrationDataNotifier
- Suppression section Nanny Registration Flow complète
- Ajout import go_router dans login_screen.dart

L'application compile maintenant sans erreurs.

Référence: #79

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/lib/config/app_router.dart

@@ -4,7 +4,6 @@ import 'package:provider/provider.dart';
 
 // Models
 import '../models/user_registration_data.dart';
-import '../models/nanny_registration_data.dart';
 import '../models/am_registration_data.dart';
 
 // Screens
@@ -15,11 +14,6 @@ import '../screens/auth/parent_register_step2_screen.dart';
 import '../screens/auth/parent_register_step3_screen.dart';
 import '../screens/auth/parent_register_step4_screen.dart';
 import '../screens/auth/parent_register_step5_screen.dart';
-import '../screens/auth/nanny_register_step1_screen.dart';
-import '../screens/auth/nanny_register_step2_screen.dart';
-import '../screens/auth/nanny_register_step3_screen.dart';
-import '../screens/auth/nanny_register_step4_screen.dart';
-import '../screens/auth/nanny_register_confirmation_screen.dart';
 import '../screens/auth/am_register_step1_screen.dart';
 import '../screens/auth/am_register_step2_screen.dart';
 import '../screens/auth/am_register_step3_screen.dart';
@@ -33,7 +27,6 @@ import '../screens/unknown_screen.dart';
 // For ShellRoute, creating them here and passing via .value is common.
 
 final userRegistrationDataNotifier = UserRegistrationData();
-final nannyRegistrationDataNotifier = NannyRegistrationData();
 final amRegistrationDataNotifier = AmRegistrationData();
 
 class AppRouter {
@@ -84,44 +77,6 @@ class AppRouter {
             path: '/parent-register-step5',
             builder: (BuildContext context, GoRouterState state) => const ParentRegisterStep5Screen(),
           ),
-          GoRoute(
-            path: '/parent-register-confirmation',
-            builder: (BuildContext context, GoRouterState state) => const NannyRegisterConfirmationScreen(),
-          ),
-        ],
-      ),
-
-      // --- Nanny Registration Flow ---
-       ShellRoute(
-        builder: (context, state, child) {
-          return ChangeNotifierProvider<NannyRegistrationData>.value(
-             value: nannyRegistrationDataNotifier,
-             child: child,
-          );
-        },
-        routes: <RouteBase>[
-          GoRoute(
-            path: '/nanny-register-step1',
-            builder: (BuildContext context, GoRouterState state) => const NannyRegisterStep1Screen(),
-          ),
-          GoRoute(
-            path: '/nanny-register-step2',
-            builder: (BuildContext context, GoRouterState state) => const NannyRegisterStep2Screen(),
-          ),
-          GoRoute(
-            path: '/nanny-register-step3',
-            builder: (BuildContext context, GoRouterState state) => const NannyRegisterStep3Screen(),
-          ),
-          GoRoute(
-            path: '/nanny-register-step4',
-            builder: (BuildContext context, GoRouterState state) => const NannyRegisterStep4Screen(),
-          ),
-           GoRoute(
-            path: '/nanny-register-confirmation',
-            builder: (BuildContext context, GoRouterState state) {
-              return const NannyRegisterConfirmationScreen();
-            },
-          ),
         ],
       ),
 

frontend/lib/screens/auth/login_screen.dart

@@ -3,6 +3,7 @@ import 'package:flutter/material.dart';
 import 'package:google_fonts/google_fonts.dart';
 import 'package:flutter/foundation.dart' show kIsWeb;
 import 'package:url_launcher/url_launcher.dart';
+import 'package:go_router/go_router.dart';
 import 'package:p_tits_pas/services/bug_report_service.dart';
 import '../../widgets/image_button.dart';
 import '../../widgets/custom_app_text_field.dart';