已按“实验成绩独立管理”完成修改。

每个实验项目独立建成绩单，支持评分项、参与状态、补做次数、安全违规、报告地址和教师评语。
流程为：录入 → 学院审核 → 教务发布；学生只能查看已发布成绩。
自主预约实验支持同步有效预约名单，已评分记录不会被误删。
课程成绩可将已发布实验成绩汇总为快照导入指定分项；导入后锁定，不能手工篡改。
实验项目成绩不完整时，对应课程分项保持空白，不按 0 分处理。
一级“实验管理”菜单下增加“项目与场次”“实验成绩”；学生端增加“实验安排”“实验成绩”。
已生成 MySQL 正式迁移及 SQLite 开发迁移，尚未操作生产数据库。
界面采用“实验项目 → 独立评分 → 审核发布”工作台设计。

src/Jiaowu.Api/Controllers/GradesController.cs

@@ -101,7 +101,9 @@ public sealed class GradesController(
                         {
                             item.Id,
                             item.Name,
-                            item.Weight
+                            item.Weight,
+                            item.SourceType,
+                            item.SourceSnapshotAt
                         }),
                         StudentCount = sheet.Records.Count,
                         CompletedCount = sheet.Records.Count(record =>
@@ -220,7 +222,9 @@ public sealed class GradesController(
                 {
                     item.Id,
                     item.Name,
-                    item.Weight
+                    item.Weight,
+                    item.SourceType,
+                    item.SourceSnapshotAt
                 }),
                 x.Status,
                 x.ReviewComment,
@@ -408,7 +412,7 @@ public sealed class GradesController(
             request.Records.Any(x => !records.ContainsKey(x.Id)))
             return ValidationProblem("包含无效或重复的成绩记录。");
 
-        var itemIds = sheet.Items.Select(item => item.Id).ToHashSet();
+        var itemsById = sheet.Items.ToDictionary(item => item.Id);
         foreach (var item in request.Records)
         {
             if (!ValidScore(item.RegularScore) ||
@@ -428,8 +432,19 @@ public sealed class GradesController(
                 {
                     if (!ValidScore(scoreEntry.Score))
                         return ValidationProblem("分项成绩必须在 0—100 分之间。");
-                    if (scoreMap.TryGetValue(scoreEntry.GradeItemId, out var existing))
-                        existing.Score = scoreEntry.Score;
+                    if (!itemsById.TryGetValue(
+                            scoreEntry.GradeItemId,
+                            out var gradeItem) ||
+                        !scoreMap.TryGetValue(
+                            scoreEntry.GradeItemId,
+                            out var existing))
+                        continue;
+                    if (gradeItem.SourceType ==
+                            GradeItemSourceType.ExperimentSummary &&
+                        existing.Score != scoreEntry.Score)
+                        return ConflictProblem(
+                            $"“{gradeItem.Name}”来自实验成绩快照，不能手工修改；请重新导入实验成绩。");
+                    existing.Score = scoreEntry.Score;
                 }
             }
 
@@ -438,6 +453,66 @@ public sealed class GradesController(
         return await SaveAsync(id, false, cancellationToken);
     }
 
+    [HttpPost("sheets/{id:guid}/import-experiment-scores")]
+    [Authorize(Roles = SheetUsers)]
+    public async Task<ActionResult> ImportExperimentScores(
+        Guid id,
+        ImportExperimentScoresRequest request,
+        CancellationToken cancellationToken)
+    {
+        var sheet = await AccessibleSheets()
+            .Include(x => x.Items)
+            .Include(x => x.Records)
+            .ThenInclude(x => x.ItemScores)
+            .Include(x => x.TeachingTask)
+            .ThenInclude(x => x!.Teachers)
+            .ThenInclude(x => x.Teacher)
+            .FirstOrDefaultAsync(x => x.Id == id, cancellationToken);
+        if (sheet is null) return NotFound();
+        if (!CanEditScores(sheet.TeachingTask!)) return Forbid();
+        if (sheet.Status is not (
+                GradeSheetStatus.Draft or
+                GradeSheetStatus.Returned))
+            return ConflictProblem("成绩单提交后不能导入实验成绩。");
+
+        var targetItem = sheet.Items.FirstOrDefault(x =>
+            x.Id == request.GradeItemId);
+        if (targetItem is null)
+            return ValidationProblem("请选择当前成绩单中的有效分项。");
+
+        var aggregate = await ExperimentGradeAggregationService.CalculateAsync(
+            db,
+            sheet.TeachingTaskId,
+            sheet.Records.Select(x => x.StudentId).ToArray(),
+            cancellationToken);
+        if (aggregate.PublishedProjectCount == 0)
+            return ConflictProblem(
+                "该教学任务尚无已发布的实验项目成绩，无法导入。");
+
+        var imported = 0;
+        var missing = 0;
+        foreach (var record in sheet.Records)
+        {
+            var targetScore = record.ItemScores.First(x =>
+                x.GradeItemId == targetItem.Id);
+            targetScore.Score = aggregate.Scores[record.StudentId];
+            if (targetScore.Score.HasValue) imported++;
+            else missing++;
+            Recalculate(sheet, record);
+        }
+        targetItem.SourceType = GradeItemSourceType.ExperimentSummary;
+        targetItem.SourceSnapshotAt = DateTime.UtcNow;
+        await db.SaveChangesAsync(cancellationToken);
+        return Ok(new
+        {
+            aggregate.PublishedProjectCount,
+            aggregate.Projects,
+            ImportedCount = imported,
+            MissingCount = missing,
+            targetItem.SourceSnapshotAt
+        });
+    }
+
     [HttpPost("sheets/{id:guid}/submit")]
     [Authorize(Roles = SheetUsers)]
     public async Task<ActionResult> Submit(Guid id, CancellationToken cancellationToken)
@@ -998,5 +1073,7 @@ public sealed record GradeItemScoreRequest(
     Guid GradeItemId,
     decimal? Score);
 
+public sealed record ImportExperimentScoresRequest(Guid GradeItemId);
+
 public sealed record GradeReviewRequest(
     [MaxLength(500)] string? Comment);