Добавил домен

backend/UniVerse.Domain/Entities/CoinTransaction.cs

@@ -0,0 +1,20 @@
+using UniVerse.Domain.Enums;
+
+namespace UniVerse.Domain.Entities;
+
+public class CoinTransaction
+{
+    public int Id { get; set; }
+    public int UserId { get; set; }
+    public int Amount { get; set; }
+    public CoinTransactionType Type { get; set; }
+    public int? ReviewId { get; set; }
+    public int? AchievementId { get; set; }
+    public string? Description { get; set; }
+    public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
+
+    // Navigation properties
+    public User User { get; set; } = null!;
+    public Review? Review { get; set; }
+    public Achievement? Achievement { get; set; }
+}