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/Shared/ManageNavMenu.razor

@@ -9,11 +9,8 @@
         <NavLink class="nav-link" href="Account/Manage/Class">Class</NavLink>
     </li>
     <li class="nav-item">
-        <NavLink class="nav-link" href="Account/Manage/ChangePassword">Password</NavLink>
+        <NavLink class="nav-link" href="Account/Manage/ChangePassword">重设密码</NavLink>
     </li>
-@*     <li class="nav-item">
-        <NavLink class="nav-link" href="Account/Manage/TwoFactorAuthentication">Two-factor authentication</NavLink>
-    </li> *@
 </ul>
 
 @code {