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

TechHelper.Client/Exam/AssignmentCheckData.cs

@@ -14,7 +14,7 @@ namespace TechHelper.Client.Exam
 	public class AssignmentCheckQuestion
 	{
 		public string Sequence { get; set; } = string.Empty;
-		public AssignmentQuestionDto AssignmentQuestionDto { get; set; } = new AssignmentQuestionDto();
+		public ExamQuestionDto ExamQuestionDto { get; set; } = new ExamQuestionDto();
 		public float Score { get; set; }
 	}
 
@@ -42,7 +42,7 @@ namespace TechHelper.Client.Exam
 
 	public static class ExamStructExtensions
 	{
-		public static AssignmentCheckData GetStruct(this AssignmentDto dto)
+		public static AssignmentCheckData GetStruct(this ExamDto dto)
 		{
 			if (dto == null)
 			{
@@ -66,7 +66,7 @@ namespace TechHelper.Client.Exam
 		/// <param name="parentSequence">当前题目组的父级序号（例如："1", "2.1"）。如果为空，则表示顶级题目组。</param>
 		/// <param name="allQuestions">用于收集所有生成题目项的列表。</param>
 		private static void GetSeqRecursive(
-			AssignmentQuestionDto currentGroup,
+			ExamQuestionDto currentGroup,
 			string? parentSequence,
 			List<AssignmentCheckQuestion> allQuestions)
 		{
@@ -74,7 +74,7 @@ namespace TechHelper.Client.Exam
 										? $"{parentSequence}.{currentGroup.Index}"
 										: currentGroup.Index.ToString();
 
-			foreach (var subGroup in currentGroup.ChildrenAssignmentQuestion)
+			foreach (var subGroup in currentGroup.ChildExamQuestions)
 			{
 				GetSeqRecursive(subGroup, currentGroupSequence, allQuestions);
 			}
@@ -83,7 +83,7 @@ namespace TechHelper.Client.Exam
 
 				allQuestions.Add(new AssignmentCheckQuestion
 				{
-					AssignmentQuestionDto = currentGroup,
+					ExamQuestionDto = currentGroup,
 					//Sequence = currentGroupSequence,
 					Sequence = currentGroup.Sequence,
 					Score = currentGroup.Score,