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backend/F9WebAiTest.Domain/Entities/IDomainEvent.cs

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+using MediatR;
+
+namespace F9WebAiTest.Domain.Entities;
+
+/// <summary>领域事件接口（继承 MediatR 的 INotification，便于事件总线发布）</summary>
+public interface IDomainEvent : INotification
+{
+    DateTime OccurredOn { get; }
+}
+
+/// <summary>领域事件基类</summary>
+public abstract record DomainEvent : IDomainEvent
+{
+    public DateTime OccurredOn => DateTime.Now;
+}