新增 PublishedScheduleOccurrences：发布时将周期规则按实际周次展开为只读课次明细。

明细保留课表版本、学期、来源排课条目、教学任务、场地、周次、星期和节次，并建立面向教学任务/周次、课表/场地/周次的索引。
明细在“发布课表”的同一事务内生成；发布失败不会留下半成品。

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

@@ -33,6 +33,7 @@ public sealed class AppDbContext(DbContextOptions<AppDbContext> options)
         Set<TeacherCourseApplication>();
     public DbSet<SchedulePlan> SchedulePlans => Set<SchedulePlan>();
     public DbSet<ScheduleEntry> ScheduleEntries => Set<ScheduleEntry>();
+    public DbSet<PublishedScheduleOccurrence> PublishedScheduleOccurrences => Set<PublishedScheduleOccurrence>();
     public DbSet<ScheduleTimeSlot> ScheduleTimeSlots => Set<ScheduleTimeSlot>();
     public DbSet<TeachingTaskScheduleConstraint> TeachingTaskScheduleConstraints =>
         Set<TeachingTaskScheduleConstraint>();
@@ -539,6 +540,15 @@ public sealed class AppDbContext(DbContextOptions<AppDbContext> options)
                 .HasForeignKey(x => x.ClassroomId)
                 .OnDelete(DeleteBehavior.Restrict);
         });
+        builder.Entity<PublishedScheduleOccurrence>(entity =>
+        {
+            entity.HasIndex(x => new { x.AcademicTermId, x.TeachingTaskId, x.Week });
+            entity.HasIndex(x => new { x.SchedulePlanId, x.ClassroomId, x.Week, x.DayOfWeek, x.StartPeriod });
+            entity.HasIndex(x => new { x.ScheduleEntryId, x.Week }).IsUnique();
+            entity.HasOne(x => x.ScheduleEntry).WithMany().HasForeignKey(x => x.ScheduleEntryId).OnDelete(DeleteBehavior.Cascade);
+            entity.HasOne(x => x.TeachingTask).WithMany().HasForeignKey(x => x.TeachingTaskId).OnDelete(DeleteBehavior.Restrict);
+            entity.HasOne(x => x.Classroom).WithMany().HasForeignKey(x => x.ClassroomId).OnDelete(DeleteBehavior.SetNull);
+        });
 
         builder.Entity<TeachingTaskAllowedExperimentClassroom>(entity =>
         {