Refactor. Add data layer

BudgetApp.Data/Interfaces/ITransactionRepository.cs

@@ -0,0 +1,20 @@
+using BudgetApp.Data.Entities;
+
+namespace BudgetApp.Data.Interfaces;
+
+public interface ITransactionRepository
+{
+    Task<List<Transaction>> GetTransactionsAsync(string userId);
+    Task<List<Transaction>> GetRecentTransactionsAsync(string userId, int count = 5);
+    Task<List<Transaction>> GetUpcomingTransactionsAsync(string userId, int count = 5);
+    Task<List<Transaction>> GetTransactionsInRangeAsync(string userId, DateTime from, DateTime to);
+    Task<List<Transaction>> GetTransactionsByAccountAsync(int accountId, string userId);
+    Task CreateTransactionAsync(Transaction transaction);
+    Task UpdateTransactionAsync(int id, string userId, string description, decimal amount, DateTime date,
+        TransactionType type, int accountId, int? categoryId,
+        RecurrenceType recurrenceType = RecurrenceType.None, DateTime? recurrenceEndDate = null);
+    Task DeleteTransactionAsync(int id, string userId);
+    Task DeleteTransactionSeriesAsync(int id, string userId);
+    Task MarkAsPaidAsync(int id, string userId, bool isPaid = true);
+    Task MaterializeRecurringTransactionsAsync(string userId, DateTime? windowEnd = null);
+}