更新功能和文档: 增强支付系统、任务队列管理、用户作品管理等功能

demo/src/main/java/com/example/demo/model/User.java

@@ -1,17 +1,18 @@
 package com.example.demo.model;
 
+import java.time.LocalDateTime;
+
 import jakarta.persistence.Column;
 import jakarta.persistence.Entity;
 import jakarta.persistence.GeneratedValue;
 import jakarta.persistence.GenerationType;
 import jakarta.persistence.Id;
-import jakarta.persistence.Table;
 import jakarta.persistence.PrePersist;
+import jakarta.persistence.Table;
 import jakarta.validation.constraints.Email;
 import jakarta.validation.constraints.Min;
 import jakarta.validation.constraints.NotBlank;
 import jakarta.validation.constraints.Size;
-import java.time.LocalDateTime;
 
 @Entity
 @Table(name = "users")
@@ -31,9 +32,7 @@ public class User {
     @Column(nullable = false, unique = true, length = 100)
     private String email;
 
-    @NotBlank
-    @Size(min = 6, max = 100)
-    @Column(nullable = false)
+    @Column(nullable = true)
     private String passwordHash;
 
     @NotBlank