feat(frontend): add restitution selection screen

eme-frontend/lib/screens/home_screen.dart

@@ -6,17 +6,12 @@ import "../widgets/profile_card.dart";
 import "../widgets/action_card.dart";
 import "../widgets/brand_corners.dart";
 import "catalogue_screen.dart";
+import "restitution_select_screen.dart";
 
 /// Écran d'accueil étudiant : profil + choix Emprunter / Restituer.
 class HomeScreen extends StatelessWidget {
   const HomeScreen({super.key});
 
-  void _bientot(BuildContext context, String action) {
-    ScaffoldMessenger.of(context).showSnackBar(
-      SnackBar(content: Text("$action — écran à venir")),
-    );
-  }
-
   @override
   Widget build(BuildContext context) {
     return Scaffold(
@@ -93,7 +88,9 @@ class HomeScreen extends StatelessWidget {
                                       description:
                                           "Restituer un matériel que vous avez emprunté",
                                       color: EnsupColors.teal,
-                                      onTap: () => _bientot(context, "Restituer"),
+                                      onTap: () => Navigator.of(context).push(
+                                        MaterialPageRoute(builder: (_) => const RestitutionSelectScreen()),
+                                      ),
                                     ),
                                   ),
                                 ],