feat(#112): reprise après refus via lien e-mail (/reprise?token=)

Branche le flux front : chargement du dossier, session reprise, wizards
parent/AM préremplis et resoumission via reprise-resoumettre.

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

frontend/lib/config/app_router.dart

@@ -21,6 +21,7 @@ import '../screens/auth/am_register_step4_screen.dart';
 import '../screens/auth/create_password_screen.dart';
 import '../screens/auth/forgot_password_screen.dart';
 import '../screens/auth/reset_password_screen.dart';
+import '../screens/auth/reprise_entry_screen.dart';
 import '../screens/home/home_screen.dart';
 import '../screens/administrateurs/admin_dashboardScreen.dart';
 import '../screens/gestionnaire/gestionnaire_dashboard_screen.dart';
@@ -66,6 +67,11 @@ class AppRouter {
         builder: (BuildContext context, GoRouterState state) =>
             ResetPasswordScreen(token: state.uri.queryParameters['token']),
       ),
+      GoRoute(
+        path: '/reprise',
+        builder: (BuildContext context, GoRouterState state) =>
+            RepriseEntryScreen(token: state.uri.queryParameters['token']),
+      ),
       GoRoute(
         path: '/home',
         builder: (BuildContext context, GoRouterState state) => const HomeScreen(),