implemented backend wallet service connection

frontend/pshared/lib/data/dto/wallet/balance.dart

@@ -0,0 +1,24 @@
+import 'package:json_annotation/json_annotation.dart';
+
+import 'package:pshared/data/dto/wallet/money.dart';
+
+part 'balance.g.dart';
+
+
+@JsonSerializable()
+class WalletBalanceDTO {
+  final MoneyDTO? available;
+  final MoneyDTO? pendingInbound;
+  final MoneyDTO? pendingOutbound;
+  final String? calculatedAt;
+
+  const WalletBalanceDTO({
+    required this.available,
+    required this.pendingInbound,
+    required this.pendingOutbound,
+    required this.calculatedAt,
+  });
+
+  factory WalletBalanceDTO.fromJson(Map<String, dynamic> json) => _$WalletBalanceDTOFromJson(json);
+  Map<String, dynamic> toJson() => _$WalletBalanceDTOToJson(this);
+}