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

Entities/DTO/User/UserDto.cs

@@ -0,0 +1,129 @@
+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
+{
+    /// <summary>
+    /// 用户信息数据传输对象
+    /// 用于在API调用中传输用户的基本信息
+    /// </summary>
+    public record UserDto
+    {
+        /// <summary>
+        /// 用户唯一标识符
+        /// </summary>
+        public Guid Id { get; init; }
+
+        /// <summary>
+        /// 用户名
+        /// </summary>
+        public string? UserName { get; init; }
+
+        /// <summary>
+        /// 电子邮箱
+        /// </summary>
+        [EmailAddress]
+        public string? Email { get; init; }
+
+        /// <summary>
+        /// 手机号码
+        /// </summary>
+        [Phone]
+        public string? PhoneNumber { get; init; }
+
+        /// <summary>
+        /// 显示名称
+        /// </summary>
+        public string? DisplayName { get; init; }
+
+        /// <summary>
+        /// 家庭住址
+        /// </summary>
+        public string? HomeAddress { get; init; }
+
+        /// <summary>
+        /// 用户角色
+        /// </summary>
+        public UserRoles? Role { get; init; }
+
+        /// <summary>
+        /// 教授科目ID
+        /// </summary>
+        public Guid? TeachSubjectId { get; init; }
+
+        /// <summary>
+        /// 教授科目信息
+        /// </summary>
+        public SubjectDto? TeachSubject { get; init; }
+
+        /// <summary>
+        /// 用户加入的班级数量
+        /// </summary>
+        public int JoinedClassCount { get; init; }
+
+        /// <summary>
+        /// 创建的问题数量
+        /// </summary>
+        public int CreatedQuestionsCount { get; init; }
+
+        /// <summary>
+        /// 创建的考试数量
+        /// </summary>
+        public int CreatedExamsCount { get; init; }
+
+        /// <summary>
+        /// 提交的作业数量
+        /// </summary>
+        public int SubmittedAssignmentsCount { get; init; }
+
+        /// <summary>
+        /// 批改的作业数量
+        /// </summary>
+        public int GradedAssignmentsCount { get; init; }
+
+        /// <summary>
+        /// 用户创建时间
+        /// </summary>
+        public DateTime CreatedAt { get; init; }
+
+        /// <summary>
+        /// 用户最后更新时间
+        /// </summary>
+        public DateTime UpdatedAt { get; init; }
+
+        /// <summary>
+        /// 用户是否已验证邮箱
+        /// </summary>
+        public bool EmailConfirmed { get; init; }
+
+        /// <summary>
+        /// 用户是否已锁定
+        /// </summary>
+        public bool LockoutEnabled { get; init; }
+
+        /// <summary>
+        /// 用户锁定结束时间
+        /// </summary>
+        public DateTime? LockoutEnd { get; init; }
+
+        /// <summary>
+        /// 获取用户角色的显示名称
+        /// </summary>
+        public string? RoleDisplayName => Role?.GetDisplayName();
+
+        /// <summary>
+        /// 获取用户角色的简短名称
+        /// </summary>
+        public string? RoleShortName => Role?.GetShortName();
+
+        /// <summary>
+        /// 获取用户的基本信息字符串
+        /// </summary>
+        public string? UserInfoString => $"{DisplayName ?? UserName} ({Email})";
+    }
+}