[#101] [Frontend] Inscription parent — API, soumission et validation

Squash merge de develop vers master.

Livrables principaux (ticket #101 et mise au point associée) :
- Branchement du formulaire d'inscription parent sur POST /api/v1/auth/register/parent
- Payload DTO (parents, enfants, photos base64, CGU) et services Auth
- Parcours gestionnaire : cartes dossiers, wizard validation famille, images authentifiées
- Scripts d'inscription test (Martin, Durand/Rousseau, Lecomte) ; .gitignore .cursor/

Inclut également les ajustements develop fusionnés dans ce lot (inscription AM, champs relais, etc.).

Closes #101

Made-with: Cursor

frontend/lib/screens/auth/parent_register_step2_screen.dart

@@ -3,7 +3,6 @@ import 'package:provider/provider.dart';
 import 'package:go_router/go_router.dart';
 
 import '../../models/user_registration_data.dart';
-import '../../utils/data_generator.dart';
 import '../../widgets/personal_info_form_screen.dart';
 import '../../models/card_assets.dart';
 
@@ -19,21 +18,17 @@ class ParentRegisterStep2Screen extends StatelessWidget {
     bool hasParent2 = parent2 != null;
     bool sameAddress = false;
     
-    // Générer des données de test si vide
     PersonalInfoData initialData;
     if (parent2 == null || parent2.firstName.isEmpty) {
-      final genFirstName = DataGenerator.firstName();
-      final genLastName = DataGenerator.lastName();
-      sameAddress = DataGenerator.boolean();
-      
+      sameAddress = false;
       initialData = PersonalInfoData(
-        firstName: genFirstName,
-        lastName: genLastName,
-        phone: DataGenerator.phone(),
-        email: DataGenerator.email(genFirstName, genLastName),
-        address: sameAddress ? parent1.address : DataGenerator.address(),
-        postalCode: sameAddress ? parent1.postalCode : DataGenerator.postalCode(),
-        city: sameAddress ? parent1.city : DataGenerator.city(),
+        firstName: parent2?.firstName ?? '',
+        lastName: parent2?.lastName ?? '',
+        phone: parent2?.phone ?? '',
+        email: parent2?.email ?? '',
+        address: parent2?.address ?? '',
+        postalCode: parent2?.postalCode ?? '',
+        city: parent2?.city ?? '',
       );
     } else {
       sameAddress = (parent2.address == parent1.address &&