后台完成修复，初始化项目

src/main/java/com/org/flashsalesystem/entity/User.java

@@ -0,0 +1,68 @@
+package com.org.flashsalesystem.entity;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import javax.persistence.*;
+import javax.validation.constraints.Email;
+import javax.validation.constraints.NotBlank;
+import javax.validation.constraints.Size;
+import java.time.LocalDateTime;
+
+/**
+ * 用户实体类
+ * 对应数据库users表
+ */
+@Entity
+@Table(name = "users")
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+public class User {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+    @NotBlank(message = "用户名不能为空")
+    @Size(min = 3, max = 50, message = "用户名长度必须在3-50个字符之间")
+    @Column(unique = true, nullable = false, length = 50)
+    private String username;
+
+    @NotBlank(message = "密码不能为空")
+    @Size(min = 6, max = 100, message = "密码长度必须在6-100个字符之间")
+    @Column(nullable = false, length = 100)
+    private String password;
+
+    @Email(message = "邮箱格式不正确")
+    @Column(length = 100)
+    private String email;
+
+    @Size(max = 20, message = "手机号长度不能超过20个字符")
+    @Column(length = 20)
+    private String phone;
+
+    @Column(name = "status", nullable = false)
+    private Integer status = 1; // 1-正常, 0-禁用
+
+    @Column(name = "last_login")
+    private LocalDateTime lastLogin;
+
+    @Column(name = "created_at", nullable = false, updatable = false)
+    private LocalDateTime createdAt;
+
+    @Column(name = "updated_at")
+    private LocalDateTime updatedAt;
+
+    @PrePersist
+    protected void onCreate() {
+        createdAt = LocalDateTime.now();
+        updatedAt = LocalDateTime.now();
+    }
+
+    @PreUpdate
+    protected void onUpdate() {
+        updatedAt = LocalDateTime.now();
+    }
+}