feat(frontend): connect borrow flow to api

eme-frontend/lib/models/emprunt_response.dart

@@ -0,0 +1,28 @@
+import "materiel_item.dart";
+
+/// Réponse renvoyée par l'API après création d'un emprunt.
+class EmpruntResponse {
+  const EmpruntResponse({
+    required this.id,
+    required this.dateEmprunt,
+    required this.dateRetourPrevue,
+    required this.statut,
+    required this.materiel,
+  });
+
+  factory EmpruntResponse.fromJson(Map<String, dynamic> json) {
+    return EmpruntResponse(
+      id: json["id"] as int,
+      dateEmprunt: DateTime.parse(json["dateEmprunt"] as String),
+      dateRetourPrevue: DateTime.parse(json["dateRetourPrevue"] as String),
+      statut: json["statut"] as String,
+      materiel: MaterielItem.fromJson(json["materiel"] as Map<String, dynamic>),
+    );
+  }
+
+  final int id;
+  final DateTime dateEmprunt;
+  final DateTime dateRetourPrevue;
+  final String statut;
+  final MaterielItem materiel;
+}