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

Entities/DTO/QuestionType/CreateQuestionTypeDto.cs

@@ -0,0 +1,19 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace Entities.DTO
+{
+    public class CreateQuestionTypeDto
+    {
+        [Required(ErrorMessage = "题型名称是必填项。")]
+        [StringLength(20, ErrorMessage = "题型名称不能超过 20 个字符。")]
+        public string TypeName { get; set; }
+
+        [Required(ErrorMessage = "科目ID是必填项。")]
+        public Guid SubjectId { get; set; }
+
+        public string Description { get; set; }
+
+        [StringLength(20, ErrorMessage = "评分规则不能超过 20 个字符。")]
+        public string ScoreRule { get; set; }
+    }
+}

Entities/DTO/QuestionType/QuestionTypeDto.cs

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+using System;
+using System.ComponentModel.DataAnnotations;
+
+namespace Entities.DTO
+{
+    public class QuestionTypeDto
+    {
+        public Guid Id { get; set; }
+
+        [Required(ErrorMessage = "题型名称是必填项。")]
+        [StringLength(20, ErrorMessage = "题型名称不能超过 20 个字符。")]
+        public string Name { get; set; }
+
+        [Required(ErrorMessage = "科目ID是必填项。")]
+        public Guid SubjectId { get; set; }
+
+        public string Description { get; set; }
+
+        [StringLength(20, ErrorMessage = "评分规则不能超过 20 个字符。")]
+        public string ScoreRule { get; set; }
+    }
+}

Entities/DTO/QuestionType/QuestionTypeResponseDto.cs

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+using System;
+using System.Collections.Generic;
+
+namespace Entities.DTO
+{
+    public class QuestionTypeResponseDto
+    {
+        public Guid TypeId { get; set; }
+        public string TypeName { get; set; }
+        public Guid SubjectId { get; set; }
+        public string SubjectName { get; set; }
+        public string Description { get; set; }
+        public string ScoreRule { get; set; }
+
+        // Navigation properties for response
+        public int QuestionCount { get; set; }
+        public List<string> QuestionTitles { get; set; } = new List<string>();
+    }
+}

Entities/DTO/QuestionType/UpdateQuestionTypeDto.cs

@@ -0,0 +1,23 @@
+using System;
+using System.ComponentModel.DataAnnotations;
+
+namespace Entities.DTO
+{
+    public class UpdateQuestionTypeDto
+    {
+        [Required(ErrorMessage = "题型ID是必填项。")]
+        public Guid TypeId { get; set; }
+
+        [Required(ErrorMessage = "题型名称是必填项。")]
+        [StringLength(20, ErrorMessage = "题型名称不能超过 20 个字符。")]
+        public string TypeName { get; set; }
+
+        [Required(ErrorMessage = "科目ID是必填项。")]
+        public Guid SubjectId { get; set; }
+
+        public string Description { get; set; }
+
+        [StringLength(20, ErrorMessage = "评分规则不能超过 20 个字符。")]
+        public string ScoreRule { get; set; }
+    }
+}