implemented backend wallet service connection

frontend/pshared/lib/models/wallet/balance.dart

@@ -0,0 +1,16 @@
+import 'package:pshared/models/wallet/money.dart';
+
+
+class WalletBalance {
+  final WalletMoney? available;
+  final WalletMoney? pendingInbound;
+  final WalletMoney? pendingOutbound;
+  final DateTime? calculatedAt;
+
+  const WalletBalance({
+    required this.available,
+    required this.pendingInbound,
+    required this.pendingOutbound,
+    required this.calculatedAt,
+  });
+}