主要改动：

自动排课接口立即返回 202 + jobId
后台服务独立执行，不受浏览器关闭或前端超时影响
进度、成功、失败状态持久化到数据库
服务重启后自动恢复排队中或中断的任务
同一草稿禁止重复提交后台任务
运行期间禁止编辑、发布或删除该课表
排课结果和任务成功状态在同一事务中提交
前端每秒轮询进度，显示已处理教学班和已规划安排数

src/Jiaowu.Api/Infrastructure/Persistence/AppDbContext.cs

@@ -36,6 +36,8 @@ public sealed class AppDbContext(DbContextOptions<AppDbContext> options)
         Set<TeachingTaskScheduleConstraint>();
     public DbSet<TeachingTaskAllowedClassroom> TeachingTaskAllowedClassrooms =>
         Set<TeachingTaskAllowedClassroom>();
+    public DbSet<AutomaticScheduleJob> AutomaticScheduleJobs =>
+        Set<AutomaticScheduleJob>();
     public DbSet<CourseSelectionRound> CourseSelectionRounds =>
         Set<CourseSelectionRound>();
     public DbSet<CourseSelectionOffering> CourseSelectionOfferings =>
@@ -381,6 +383,23 @@ public sealed class AppDbContext(DbContextOptions<AppDbContext> options)
                 .OnDelete(DeleteBehavior.Restrict);
         });
 
+        builder.Entity<AutomaticScheduleJob>(entity =>
+        {
+            entity.Property(x => x.ErrorMessage).HasMaxLength(2000);
+            entity.HasIndex(x => x.ActiveSchedulePlanId).IsUnique();
+            entity.HasIndex(x => new { x.SchedulePlanId, x.CreatedAt });
+            entity.HasIndex(x => new { x.Status, x.CreatedAt });
+            entity.HasIndex(x => x.RequestedByUserId);
+            entity.HasOne(x => x.SchedulePlan)
+                .WithMany()
+                .HasForeignKey(x => x.SchedulePlanId)
+                .OnDelete(DeleteBehavior.Cascade);
+            entity.HasOne<ApplicationUser>()
+                .WithMany()
+                .HasForeignKey(x => x.RequestedByUserId)
+                .OnDelete(DeleteBehavior.SetNull);
+        });
+
         builder.Entity<CourseSelectionRound>(entity =>
         {
             entity.Property(x => x.Name).HasMaxLength(120);