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backend/F9WebAiTest.Domain/Entities/BusinessEntity.cs

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+using FreeSql.DataAnnotations;
+
+namespace F9WebAiTest.Domain.Entities;
+
+/// <summary>
+/// DDD 业务实体基类：Entity + 审计字段（CreatedBy/UpdateBy/DeletedAt）。
+/// 参考 BBIT.F9.Domain.Entities.BusinessEntity
+/// </summary>
+public abstract class BusinessEntity : Entity
+{
+    /// <summary>创建人</summary>
+    [Column(Name = "created_by")]
+    public string CreatedBy { get; set; }
+
+    /// <summary>修改人</summary>
+    [Column(Name = "update_by")]
+    public string UpdateBy { get; set; }
+
+    /// <summary>逻辑删除时间（null=未删除）</summary>
+    [Column(Name = "deleted_at")]
+    public DateTime? DeletedAt { get; protected set; }
+}