feat: Implement Parent Registration Step 4 and Step 5 Screens

- Added ParentRegisterStep4Screen for capturing motivation and CGU acceptance.
- Integrated custom checkbox and text field widgets for better UI.
- Implemented modal dialog for displaying CGU text.
- Created ParentRegisterStep5Screen for summarizing registration data.
- Added functionality to display parent and child details with edit options.
- Included confirmation modal upon submission of the registration request.

frontend/lib/screens/auth/am/am_register_step1_sceen.dart

@@ -0,0 +1,18 @@
+
+import 'package:flutter/material.dart';
+
+class AmRegisterStep1Screen extends StatelessWidget {
+  const AmRegisterStep1Screen({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(
+        title: const Text('Étape 1 - Inscription AM'),
+      ),
+      body: const  Center(
+        child: Text('Contenu de l\'étape 1'),
+      ),
+    );
+  }
+}