重构项目结构，移除Assignment相关功能，优化Submission模块

Entities/DTO/User/UserForRegistrationDto.cs

@@ -0,0 +1,43 @@
+using Entities.Contracts;
+using System;
+using System.Collections.Generic;
+using System.ComponentModel.DataAnnotations;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Entities.DTO
+{
+    public class UserForRegistrationDto
+    {
+        [Required(ErrorMessage = "姓名是必填项。")]
+        [StringLength(50, MinimumLength = 2, ErrorMessage = "姓名长度必须在 2 到 50 个字符之间。")]
+        public  string DisplayName { get; set; }
+
+        [Required(ErrorMessage = "电子邮件是必填项。")]
+        [EmailAddress(ErrorMessage = "电子邮件格式不正确。")]
+        public  string Email { get; set; }
+
+        [Required(ErrorMessage = "密码是必填项。")]
+        [StringLength(100, MinimumLength = 6, ErrorMessage = "密码长度至少为 6 个字符。")]
+        [RegularExpression(@"^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[@$!%*?&.])[A-Za-z\d@$!%*?&.]{6,}$",
+         ErrorMessage = "密码必须包含至少一个大写字母、一个小写字母、一个数字和一个特殊字符。特殊字符包含 @$!%*?&. ")]
+        public  string Password { get; set; }
+
+        [Compare(nameof(Password), ErrorMessage = "密码和确认密码不匹配。")]
+        [Required(ErrorMessage = "确认密码是必填项。")]
+        public  string ConfirmPassword { get; set; }
+
+        [Required(ErrorMessage = "至少选择一个角色。")]
+        public UserRoles Roles { get; set; } = UserRoles.Student;
+
+        [Phone(ErrorMessage = "电话号码格式不正确。")]
+        [StringLength(11, MinimumLength = 11, ErrorMessage = "电话号码必须是 11 位数字。")]
+        public string? PhoneNumber { get; set; }
+
+        [StringLength(200, ErrorMessage = "家庭住址不能超过 200 个字符。")]
+        public string? HomeAddress { get; set; }
+
+        public RegisterUserToClassDto RegisterUserToClassDto { get; set; } = new RegisterUserToClassDto();
+    }
+}