feat: Add User and UserBalance models with serialization methods

feat: Implement BalanceRepository for group balance calculations

feat: Create ExpenseRepository for managing expenses

feat: Add services for handling expenses and storage operations

fix: Update import paths for models in repositories and services

refactor: Rename CountContent to AccountContent in HomePage

chore: Add StorageService for image upload and management

lib/blocs/expense/expense_state.dart

@@ -0,0 +1,44 @@
+import 'package:equatable/equatable.dart';
+import '../../models/expense.dart';
+
+abstract class ExpenseState extends Equatable {
+  const ExpenseState();
+
+  @override
+  List<Object?> get props => [];
+}
+
+class ExpenseInitial extends ExpenseState {}
+
+class ExpenseLoading extends ExpenseState {}
+
+class ExpensesLoaded extends ExpenseState {
+  final List<Expense> expenses;
+  final Map<String, double> exchangeRates;
+
+  const ExpensesLoaded({
+    required this.expenses,
+    this.exchangeRates = const {'EUR': 1.0, 'USD': 0.85, 'GBP': 1.15},
+  });
+
+  @override
+  List<Object?> get props => [expenses, exchangeRates];
+}
+
+class ExpenseOperationSuccess extends ExpenseState {
+  final String message;
+
+  const ExpenseOperationSuccess(this.message);
+
+  @override
+  List<Object?> get props => [message];
+}
+
+class ExpenseError extends ExpenseState {
+  final String message;
+
+  const ExpenseError(this.message);
+
+  @override
+  List<Object?> get props => [message];
+}