[#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_step1_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';
 
@@ -15,31 +14,15 @@ class ParentRegisterStep1Screen extends StatelessWidget {
     final registrationData = Provider.of<UserRegistrationData>(context, listen: false);
     final parent1 = registrationData.parent1;
     
-    // Générer des données de test si vide
-    PersonalInfoData initialData;
-    if (parent1.firstName.isEmpty) {
-      final genFirstName = DataGenerator.firstName();
-      final genLastName = DataGenerator.lastName();
-      initialData = PersonalInfoData(
-        firstName: genFirstName,
-        lastName: genLastName,
-        phone: DataGenerator.phone(),
-        email: DataGenerator.email(genFirstName, genLastName),
-        address: DataGenerator.address(),
-        postalCode: DataGenerator.postalCode(),
-        city: DataGenerator.city(),
-      );
-    } else {
-      initialData = PersonalInfoData(
-        firstName: parent1.firstName,
-        lastName: parent1.lastName,
-        phone: parent1.phone,
-        email: parent1.email,
-        address: parent1.address,
-        postalCode: parent1.postalCode,
-        city: parent1.city,
-      );
-    }
+    final initialData = PersonalInfoData(
+      firstName: parent1.firstName,
+      lastName: parent1.lastName,
+      phone: parent1.phone,
+      email: parent1.email,
+      address: parent1.address,
+      postalCode: parent1.postalCode,
+      city: parent1.city,
+    );
 
     return PersonalInfoFormScreen(
       stepText: 'Étape 1/5',