Add saved payout destination UX and service contracts (#54)

frontend/app/lib/routing/router.dart

@@ -7,6 +7,7 @@ import 'package:go_router/go_router.dart';
 import 'package:sxchnge_wallet/sxchnge_wallet.dart';
 
 import '../auth/page.dart';
+import '../destinations/list.dart';
 import '../kyc/page.dart';
 import '../security/challenge.dart';
 import '../verification/page.dart';
@@ -82,6 +83,12 @@ GoRouter createAppRouter({bool Function()? authenticated}) {
           GoRoute(
             path: '/settings',
             builder: (context, state) => const SettingsPage(),
+            routes: [
+              GoRoute(
+                path: 'payout-methods',
+                builder: (context, state) => const DestinationsPage(),
+              ),
+            ],
           ),
           GoRoute(
             path: '/top-up',