Add initial project structure and configuration files for iOS and Android

lib/features/transactions/models/transaction.dart

@@ -0,0 +1,15 @@
+class Transaction {
+  final String id;
+  final String description;
+  final double amount;
+  final DateTime date;
+  final String category;
+  
+  Transaction({
+    required this.id,
+    required this.description,
+    required this.amount,
+    required this.date,
+    required this.category,
+  });
+}