feat(#112): reprise après refus — dossier complet, email resoumission

- GET/PATCH reprise-dossier enrichis (parents, enfants, motivation, fiche AM)
- Front: lien mail, modale identify login, wizards préremplis, PATCH complet
- Email accusé resoumission aux parents avec n° de dossier
- Fixes préremplissage AM (dates, places, ValueKey étape 2)

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

frontend/lib/services/reprise_session.dart

@@ -0,0 +1,58 @@
+import 'package:p_tits_pas/models/am_registration_data.dart';
+import 'package:p_tits_pas/models/reprise_dossier.dart';
+import 'package:p_tits_pas/models/user_registration_data.dart';
+import 'package:p_tits_pas/services/api/api_config.dart';
+import 'package:p_tits_pas/utils/reprise_mapper.dart';
+
+/// Contexte reprise après refus (token e-mail ou identify). Ticket #112.
+class RepriseSession {
+  RepriseSession._();
+
+  static String? _token;
+  static String? _role;
+  static String? _photoUrl;
+  static String? _photoUrlForApi;
+
+  static bool get isActive =>
+      _token != null && _token!.trim().isNotEmpty;
+
+  static String? get token => _token;
+
+  static bool get isParent => _role == 'parent';
+
+  static bool get isAm => _role == 'assistante_maternelle';
+
+  /// URL absolue pour l'affichage.
+  static String? get photoUrl => _photoUrl;
+
+  /// Chemin relatif API (`/uploads/…`) pour PATCH sans re-upload.
+  static String? get photoUrlForApi => _photoUrlForApi;
+
+  static void start({
+    required String token,
+    required RepriseDossier dossier,
+  }) {
+    _token = token.trim();
+    _role = dossier.role;
+    final raw = dossier.photoUrl?.trim();
+    _photoUrlForApi = raw != null && raw.isNotEmpty ? raw : null;
+    _photoUrl = _photoUrlForApi != null
+        ? ApiConfig.absoluteMediaUrl(_photoUrlForApi)
+        : null;
+  }
+
+  static void clear() {
+    _token = null;
+    _role = null;
+    _photoUrl = null;
+    _photoUrlForApi = null;
+  }
+
+  static void applyToParent(UserRegistrationData data, RepriseDossier dossier) {
+    RepriseMapper.applyParentDossier(data, dossier);
+  }
+
+  static void applyToAm(AmRegistrationData data, RepriseDossier dossier) {
+    RepriseMapper.applyAmDossier(data, dossier);
+  }
+}