免修、缓考现在包含当前学期课程，以及未归档且课表已发布的实际修读课程。

实际开发库验证已返回 CS101 程序设计基础。
课程替代改为“修读中/未通过课程 → 已发布及格课程”的双栏选择。
新增搜索、教学班号、学期、教师、学分、课表状态和完整空状态说明。
新增课程替代申请记录。
提交接口增加服务端资格校验，不能伪造课程 ID 绕过前端。

src/Jiaowu.Api/Controllers/ApprovalsController.cs

@@ -80,6 +80,9 @@ public sealed class ApprovalsController(AppDbContext db, ICurrentUserDataScope s
     {
         var studentId = await GetStudentIdAsync(ct);
         if (studentId is null) return StudentNotFound();
+        if (!await IsStudentCourseAvailableForApplicationAsync(
+                studentId.Value, req.TeachingTaskId, ct))
+            return ConflictProblem("该课程不在您当前或已发布课表的修读课程中，请刷新课程列表后重试。");
         if (await db.CourseExemptions.AnyAsync(x => x.StudentId == studentId && x.TeachingTaskId == req.TeachingTaskId && x.Status == ApprovalStatus.Submitted, ct))
             return ConflictProblem("该课程已有免修申请在审核中。");
         var ex = new CourseExemption { StudentId = studentId.Value, TeachingTaskId = req.TeachingTaskId, Reason = req.Reason.Trim() };
@@ -141,6 +144,9 @@ public sealed class ApprovalsController(AppDbContext db, ICurrentUserDataScope s
     {
         var sid = await GetStudentIdAsync(ct);
         if (sid is null) return StudentNotFound();
+        if (!await IsStudentCourseAvailableForApplicationAsync(
+                sid.Value, req.TeachingTaskId, ct))
+            return ConflictProblem("该课程不在您当前或已发布课表的修读课程中，请刷新课程列表后重试。");
         if (await db.DeferredExams.AnyAsync(x => x.StudentId == sid && x.TeachingTaskId == req.TeachingTaskId && x.Status == ApprovalStatus.Submitted, ct))
             return ConflictProblem("该课程已有缓考申请在审核中。");
         var d = new DeferredExam { StudentId = sid.Value, TeachingTaskId = req.TeachingTaskId, Reason = req.Reason.Trim() };
@@ -248,12 +254,75 @@ public sealed class ApprovalsController(AppDbContext db, ICurrentUserDataScope s
     }
 
     // ═══════════════ Course Substitution ═══════════════
+    [HttpGet("substitutions/mine")]
+    [Authorize(Roles = SystemRoles.Student)]
+    public async Task<ActionResult> GetMySubstitutions(CancellationToken ct)
+    {
+        var sid = await GetStudentIdAsync(ct);
+        if (sid is null) return StudentNotFound();
+        return Ok(await db.CourseSubstitutions.AsNoTracking()
+            .Where(x => x.StudentId == sid)
+            .OrderByDescending(x => x.CreatedAt)
+            .Select(x => new StudentCourseSubstitutionRecord(
+                x.Id,
+                x.Status,
+                x.Reason,
+                x.ReviewComment,
+                x.SubmittedAt,
+                x.OriginalCourse!.Code,
+                x.OriginalCourse.Name,
+                x.SubstituteCourse!.Code,
+                x.SubstituteCourse.Name))
+            .ToListAsync(ct));
+    }
+
     [HttpPost("substitutions")]
     [Authorize(Roles = SystemRoles.Student)]
     public async Task<ActionResult> ApplySubstitution(SubstitutionRequest req, CancellationToken ct)
     {
         var sid = await GetStudentIdAsync(ct);
         if (sid is null) return StudentNotFound();
+        if (req.OriginalCourseId == req.SubstituteCourseId)
+            return ConflictProblem("被替代课程和替代课程不能相同。");
+        var isAssignedCourse = await db.TeachingTasks.AsNoTracking()
+            .AnyAsync(task =>
+                task.CourseId == req.OriginalCourseId &&
+                task.Status == TeachingTaskStatus.Published &&
+                !task.AcademicTerm!.IsArchived &&
+                (task.AcademicTerm.IsCurrent ||
+                 db.ScheduleEntries.Any(entry =>
+                     entry.TeachingTaskId == task.Id &&
+                     entry.SchedulePlan!.Status ==
+                         SchedulePlanStatus.Published)) &&
+                (task.Classes.Any(item =>
+                     item.AdministrativeClass!.Students.Any(student =>
+                         student.Id == sid.Value)) ||
+                 db.CourseEnrollments.Any(enrollment =>
+                     enrollment.StudentId == sid.Value &&
+                     enrollment.Status == CourseEnrollmentStatus.Enrolled &&
+                     enrollment.CourseSelectionOffering!.TeachingTaskId ==
+                         task.Id)),
+                ct);
+        var hasFailedOriginal = await db.GradeRecords.AsNoTracking()
+            .AnyAsync(record =>
+                record.StudentId == sid.Value &&
+                record.GradeSheet!.Status == GradeSheetStatus.Published &&
+                record.GradeSheet.TeachingTask!.CourseId ==
+                    req.OriginalCourseId &&
+                record.TotalScore < 60,
+                ct);
+        var canReplaceOriginal = isAssignedCourse || hasFailedOriginal;
+        if (!canReplaceOriginal)
+            return ConflictProblem("被替代课程必须是当前或已发布课表的修读课程，或已有未通过成绩的课程。");
+        var hasPassedSubstitute = await db.GradeRecords.AsNoTracking()
+            .AnyAsync(x =>
+                x.StudentId == sid.Value &&
+                x.GradeSheet!.Status == GradeSheetStatus.Published &&
+                x.GradeSheet.TeachingTask!.CourseId == req.SubstituteCourseId &&
+                x.TotalScore >= 60,
+                ct);
+        if (!hasPassedSubstitute)
+            return ConflictProblem("替代课程必须具有已发布且及格的成绩。");
         if (await db.CourseSubstitutions.AnyAsync(x => x.StudentId == sid && x.OriginalCourseId == req.OriginalCourseId && x.Status == ApprovalStatus.Submitted, ct))
             return ConflictProblem("该课程已有替代申请在审核中。");
         var cs = new CourseSubstitution { StudentId = sid.Value, OriginalCourseId = req.OriginalCourseId, SubstituteCourseId = req.SubstituteCourseId, Reason = req.Reason.Trim() };
@@ -319,16 +388,50 @@ public sealed class ApprovalsController(AppDbContext db, ICurrentUserDataScope s
         return NoContent();
     }
 
-    // ═══════════════ Student enrolled courses ═══════════════
+    // ═══════════════ Student course options ═══════════════
     [HttpGet("my-courses")]
     [Authorize(Roles = SystemRoles.Student)]
     public async Task<ActionResult> GetMyEnrolledCourses(CancellationToken ct)
     {
         var sid = await GetStudentIdAsync(ct);
         if (sid is null) return StudentNotFound();
-        var courses = await db.CourseEnrollments.AsNoTracking()
-            .Where(x => x.StudentId == sid && x.Status == CourseEnrollmentStatus.Enrolled)
-            .Select(x => new { x.CourseSelectionOffering!.TeachingTaskId, x.CourseSelectionOffering.TeachingTask!.TaskNumber, CourseCode = x.CourseSelectionOffering.TeachingTask.Course!.Code, CourseName = x.CourseSelectionOffering.TeachingTask.Course.Name })
+        var courses = await db.TeachingTasks.AsNoTracking()
+            .Where(task =>
+                task.Status == TeachingTaskStatus.Published &&
+                !task.AcademicTerm!.IsArchived &&
+                (task.AcademicTerm.IsCurrent ||
+                 db.ScheduleEntries.Any(entry =>
+                     entry.TeachingTaskId == task.Id &&
+                     entry.SchedulePlan!.Status ==
+                         SchedulePlanStatus.Published)) &&
+                (task.Classes.Any(item =>
+                     item.AdministrativeClass!.Students.Any(student =>
+                         student.Id == sid.Value)) ||
+                 db.CourseEnrollments.Any(enrollment =>
+                     enrollment.StudentId == sid.Value &&
+                     enrollment.Status == CourseEnrollmentStatus.Enrolled &&
+                     enrollment.CourseSelectionOffering!.TeachingTaskId ==
+                         task.Id)))
+            .OrderByDescending(x => x.AcademicTerm!.IsCurrent)
+            .ThenByDescending(x => x.AcademicTerm!.StartDate)
+            .ThenBy(x => x.Course!.Code)
+            .ThenBy(x => x.TaskNumber)
+            .Select(x => new StudentApprovalCourseOption(
+                x.Id,
+                x.CourseId,
+                x.TaskNumber,
+                x.Course!.Code,
+                x.Course.Name,
+                x.Course.Credits,
+                x.AcademicTerm!.Name,
+                x.Teachers
+                    .OrderByDescending(item => item.IsPrimary)
+                    .ThenBy(item => item.Teacher!.Name)
+                    .Select(item => item.Teacher!.Name),
+                db.ScheduleEntries.Any(entry =>
+                    entry.TeachingTaskId == x.Id &&
+                    entry.SchedulePlan!.Status == SchedulePlanStatus.Published),
+                x.SchedulingMode))
             .ToListAsync(ct);
         return Ok(courses);
     }
@@ -341,8 +444,18 @@ public sealed class ApprovalsController(AppDbContext db, ICurrentUserDataScope s
         if (sid is null) return StudentNotFound();
         var grades = await db.GradeRecords.AsNoTracking()
             .Where(x => x.StudentId == sid && x.GradeSheet!.Status == GradeSheetStatus.Published)
-            .Select(x => new { CourseId = x.GradeSheet!.TeachingTask!.CourseId, CourseCode = x.GradeSheet.TeachingTask.Course!.Code, CourseName = x.GradeSheet.TeachingTask.Course.Name, x.TotalScore, x.GradePoint, x.ExamStatus })
-            .OrderBy(x => x.CourseCode)
+            .OrderByDescending(x => x.GradeSheet!.PublishedAt)
+            .Select(x => new StudentApprovalGradeOption(
+                x.GradeSheet!.TeachingTask!.CourseId,
+                x.GradeSheet.TeachingTask.Course!.Code,
+                x.GradeSheet.TeachingTask.Course.Name,
+                x.GradeSheet.TeachingTask.Course.Credits,
+                x.TotalScore,
+                x.GradePoint,
+                x.ExamStatus,
+                x.GradeSheet.TeachingTask.AcademicTerm!.Name,
+                x.GradeSheet.TeachingTask.TaskNumber,
+                x.GradeSheet.PublishedAt))
             .ToListAsync(ct);
         return Ok(grades);
     }
@@ -377,6 +490,27 @@ public sealed class ApprovalsController(AppDbContext db, ICurrentUserDataScope s
     }
 
     private async Task<Guid?> GetStudentIdAsync(CancellationToken ct) => await db.Students.Where(s => s.UserId == scope.Current.UserId).Select(s => (Guid?)s.Id).FirstOrDefaultAsync(ct);
+    private async Task<bool> IsStudentCourseAvailableForApplicationAsync(
+        Guid studentId,
+        Guid teachingTaskId,
+        CancellationToken ct) =>
+        await db.TeachingTasks.AsNoTracking().AnyAsync(task =>
+            task.Id == teachingTaskId &&
+            task.Status == TeachingTaskStatus.Published &&
+            !task.AcademicTerm!.IsArchived &&
+            (task.AcademicTerm.IsCurrent ||
+             db.ScheduleEntries.Any(entry =>
+                 entry.TeachingTaskId == task.Id &&
+                 entry.SchedulePlan!.Status == SchedulePlanStatus.Published)) &&
+            (task.Classes.Any(item =>
+                 item.AdministrativeClass!.Students.Any(student =>
+                     student.Id == studentId)) ||
+             db.CourseEnrollments.Any(enrollment =>
+                 enrollment.StudentId == studentId &&
+                 enrollment.Status == CourseEnrollmentStatus.Enrolled &&
+                 enrollment.CourseSelectionOffering!.TeachingTaskId ==
+                     task.Id)),
+            ct);
     private ActionResult StudentNotFound() => Conflict(new ProblemDetails { Title = "未关联学生档案", Detail = "当前账号未关联有效学生档案。", Status = 409 });
 
     private async Task NotifyManagers(string title, string content, CancellationToken ct) { await NotificationService.SendToRoleAsync(db, SystemRoles.CollegeAdmin, title, content, cancellationToken: ct); await NotificationService.SendToRoleAsync(db, SystemRoles.AcademicAdmin, title, content, cancellationToken: ct); }
@@ -390,6 +524,38 @@ public sealed class ApprovalsController(AppDbContext db, ICurrentUserDataScope s
 }
 
 public sealed record ApprovalItem(Guid Id, string Type, string Label, string Title, string Desc, DateTime Time, string College);
+public sealed record StudentApprovalCourseOption(
+    Guid TeachingTaskId,
+    Guid CourseId,
+    string TaskNumber,
+    string CourseCode,
+    string CourseName,
+    decimal Credits,
+    string AcademicTermName,
+    IEnumerable<string> TeacherNames,
+    bool HasPublishedSchedule,
+    TeachingTaskSchedulingMode SchedulingMode);
+public sealed record StudentApprovalGradeOption(
+    Guid CourseId,
+    string CourseCode,
+    string CourseName,
+    decimal Credits,
+    decimal? TotalScore,
+    decimal? GradePoint,
+    GradeExamStatus ExamStatus,
+    string AcademicTermName,
+    string TaskNumber,
+    DateTime? PublishedAt);
+public sealed record StudentCourseSubstitutionRecord(
+    Guid Id,
+    ApprovalStatus Status,
+    string Reason,
+    string? ReviewComment,
+    DateTime SubmittedAt,
+    string OriginalCourseCode,
+    string OriginalCourseName,
+    string SubstituteCourseCode,
+    string SubstituteCourseName);
 public sealed record ExemptionRequest(Guid TeachingTaskId, [Required, MaxLength(500)] string Reason);
 public sealed record GradeModRequest(Guid GradeRecordId, decimal RequestedScore, [Required, MaxLength(500)] string Reason);
 public sealed record SubstitutionRequest(Guid OriginalCourseId, Guid SubstituteCourseId, [Required, MaxLength(500)] string Reason);