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/models/am_registration_data.dart

@@ -33,6 +33,9 @@ class AmRegistrationData extends ChangeNotifier {
   /// Places libres actuellement (0 ≤ valeur ≤ capacité) — API `places_disponibles`.
   int? placesAvailable;
 
+  /// Photo déjà en base lors d'une reprise (#112) — sert pour l'affichage et `photo_url` API.
+  String? repriseExistingPhotoUrl;
+
   // Step 3: Presentation & CGU
   String presentationText = '';
   bool cguAccepted = false;
@@ -104,6 +107,43 @@ class AmRegistrationData extends ChangeNotifier {
     notifyListeners();
   }
 
+  /// Reprise après refus (#112).
+  void resetForReprise({
+    required String firstName,
+    required String lastName,
+    required String phone,
+    required String email,
+    required String streetAddress,
+    required String postalCode,
+    required String city,
+    String? existingPhotoUrl,
+  }) {
+    this.firstName = firstName;
+    this.lastName = lastName;
+    this.phone = phone;
+    this.email = email;
+    this.streetAddress = streetAddress;
+    this.postalCode = postalCode;
+    this.city = city;
+    password = '';
+    repriseExistingPhotoUrl = existingPhotoUrl;
+    photoPath = existingPhotoUrl;
+    photoBytes = null;
+    photoFilename = null;
+    photoConsent = false;
+    dateOfBirth = null;
+    birthCity = '';
+    birthCountry = '';
+    nir = '';
+    agrementNumber = '';
+    agreementDate = null;
+    capacity = null;
+    placesAvailable = null;
+    presentationText = '';
+    cguAccepted = false;
+    notifyListeners();
+  }
+
   // --- Getters for validation or display ---
   bool get isStep1Complete =>
       firstName.trim().length >= 2 &&
@@ -118,6 +158,8 @@ class AmRegistrationData extends ChangeNotifier {
   /// Photo réelle (pas seulement un placeholder asset).
   bool get _hasUserPhoto =>
       (photoBytes != null && photoBytes!.isNotEmpty) ||
+      (repriseExistingPhotoUrl != null &&
+          repriseExistingPhotoUrl!.trim().isNotEmpty) ||
       (photoPath != null &&
           photoPath!.isNotEmpty &&
           !photoPath!.startsWith('assets/'));
@@ -145,6 +187,9 @@ class AmRegistrationData extends ChangeNotifier {
   bool get isRegistrationComplete =>
       isStep1Complete && isStep2Complete && isStep3Complete;
 
+  /// Reprise (#112) : champs renvoyés par PATCH reprise-resoumettre.
+  bool get isRepriseSubmitReady => isStep1Complete && cguAccepted;
+
   @override
   String toString() {
     return 'AmRegistrationData('