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

Entities/DTO/Exam/ExamResponseDto.cs

@@ -0,0 +1,34 @@
+using System;
+using System.Collections.Generic;
+
+namespace Entities.DTO
+{
+    public class ExamResponseDto
+    {
+        public Guid Id { get; set; }
+        public string Title { get; set; }
+        public string Description { get; set; }
+        public Guid SubjectId { get; set; }
+        public string SubjectName { get; set; }
+        public Guid ExamStructId { get; set; }
+        public string ExamStructName { get; set; }
+        public Guid ExamTypeId { get; set; }
+        public string ExamTypeName { get; set; }
+        public Guid CreatorId { get; set; }
+        public string CreatorName { get; set; }
+        public DateTime DueDate { get; set; }
+        public byte TotalQuestions { get; set; }
+        public float Score { get; set; }
+        public string Name { get; set; }
+        public DateTime CreatedAt { get; set; }
+        public DateTime UpdatedAt { get; set; }
+        public bool IsDeleted { get; set; }
+
+        // Navigation properties for response
+        public int AttachmentCount { get; set; }
+        public int SubmissionCount { get; set; }
+        public List<string> AttachmentNames { get; set; } = new List<string>();
+        public List<string> StudentNames { get; set; } = new List<string>();
+        public List<DateTime> SubmissionTimes { get; set; } = new List<DateTime>();
+    }
+}