feat: 添加学生提交系统功能

- 添加学生提交管理服务 (StudentSubmissionService, StudentSubmissionDetailService)
- 新增学生提交相关控制器 (StudentSubmissionController, StudentSubmissionDetailController)
- 添加学生提交数据传输对象 (StudentSubmissionDetailDto, StudentSubmissionSummaryDto)
- 新增学生提交相关页面组件 (StudentExamView, ExamDetailView, StudentCard等)
- 添加学生提交信息卡片组件 (SubmissionInfoCard, TeacherSubmissionInfoCard)
- 更新数据库迁移文件以支持提交系统

TechHelper.Client/Layout/MainLayout.razor

@@ -24,13 +24,9 @@
 				<MudNavMenu Bordered="true" Dense="true" Rounded="true" Color="Color.Error" Margin="Margin.Dense">
 					<ApplicationMainIconCard></ApplicationMainIconCard>
 					<MudDivider Class="my-2" />
-					<MudNavLink Href="/">Dashboard</MudNavLink>
+					<MudNavLink Href="/">Home</MudNavLink>
 					<MudNavLink Href="/exam">Exam</MudNavLink>
-					<MudNavLink Href="/exam">Billing</MudNavLink>
-					<MudNavGroup Title="Settings" Expanded="true">
-						<MudNavLink Href="/users">Users</MudNavLink>
-						<MudNavLink Href="/security">Security</MudNavLink>
-					</MudNavGroup>
+					<MudNavLink Href="/students">Students</MudNavLink>
 
 					<MudSpacer />
 					<MudNavLink Class="align-content-end" Href="/about">About</MudNavLink>
@@ -38,7 +34,7 @@
 				<MudSpacer />
 				<MudNavMenu Class="align-content-end " Bordered="true" Dense="true" Rounded="true" Margin="Margin.Dense">
 					<TechHelper.Client.Pages.Global.LoginInOut.LoginInOut></TechHelper.Client.Pages.Global.LoginInOut.LoginInOut>
-					<MudNavLink Class="align-content-end" Href="/about">Setting</MudNavLink>
+					<MudNavLink Class="align-content-end" Href="/Account/Manage">Setting</MudNavLink>
 				</MudNavMenu>
 			</MudPaper>
 		</MudDrawerHeader>
@@ -46,7 +42,7 @@
 	<MudMainContent Style="background: #f5f6fb">
 		<SnackErrorBoundary @ref="errorBoundary">
 			<MudPaper Height="calc(100vh - 64px)" Style="background-color:transparent" Class="overflow-hidden px-1 py-2" Elevation="0">
-				<MudPaper Style="background-color:#eeeeeeef" Elevation="3" Class="d-flex w-100 h-100 overflow-hidden pa-2 rounded-xl">
+				<MudPaper Style="background-color:transparent" Elevation="0" Class="d-flex w-100 h-100 overflow-hidden pa-2 rounded-xl">
 					@Body
 				</MudPaper>
 			</MudPaper>