add backend

backend/src/main/java/com/yoyuzh/auth/User.java

@@ -0,0 +1,84 @@
+package com.yoyuzh.auth;
+
+import jakarta.persistence.Column;
+import jakarta.persistence.Entity;
+import jakarta.persistence.GeneratedValue;
+import jakarta.persistence.GenerationType;
+import jakarta.persistence.Id;
+import jakarta.persistence.Index;
+import jakarta.persistence.PrePersist;
+import jakarta.persistence.Table;
+
+import java.time.LocalDateTime;
+
+@Entity
+@Table(name = "portal_user", indexes = {
+        @Index(name = "uk_user_username", columnList = "username", unique = true),
+        @Index(name = "uk_user_email", columnList = "email", unique = true),
+        @Index(name = "idx_user_created_at", columnList = "created_at")
+})
+public class User {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+    @Column(nullable = false, length = 64, unique = true)
+    private String username;
+
+    @Column(nullable = false, length = 128, unique = true)
+    private String email;
+
+    @Column(name = "password_hash", nullable = false, length = 255)
+    private String passwordHash;
+
+    @Column(name = "created_at", nullable = false)
+    private LocalDateTime createdAt;
+
+    @PrePersist
+    public void prePersist() {
+        if (createdAt == null) {
+            createdAt = LocalDateTime.now();
+        }
+    }
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getUsername() {
+        return username;
+    }
+
+    public void setUsername(String username) {
+        this.username = username;
+    }
+
+    public String getEmail() {
+        return email;
+    }
+
+    public void setEmail(String email) {
+        this.email = email;
+    }
+
+    public String getPasswordHash() {
+        return passwordHash;
+    }
+
+    public void setPasswordHash(String passwordHash) {
+        this.passwordHash = passwordHash;
+    }
+
+    public LocalDateTime getCreatedAt() {
+        return createdAt;
+    }
+
+    public void setCreatedAt(LocalDateTime createdAt) {
+        this.createdAt = createdAt;
+    }
+}