试用前准备：全班模拟压测、评分并发 6→16、手动备份与恢复

- test/classroom.ts：45 个虚拟学生走一遍登录、运行、自测、提交，统计每个环节等多久
- 评分并发可配置（SIM_GRADE_CONCURRENCY，默认 16），提交队列同时评的份数跟着走；
  2 核实测项目 8 任务 3 全班自测从约 4 分钟降到约 1.5 分钟
- 检查的默认等待 2 秒→5 秒，机器忙时不再误判正确的程序
- 删除学生时删除他的数据库（编号会重新用给新学生）
- deploy/backup.sh、deploy/restore.sh：手动备份到宿主机 backups/，恢复前先备份

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

samples/p8-t5-历史图片/checks.yaml

@@ -5,7 +5,7 @@
   steps:
     - clock: '09:00:00'
     - click: pic_security
-    - expect: { control: pic_video, image: true, within: 3s }
+    - expect: { control: pic_video, image: true }
     - click: btn_camera
     - click: btn_history
     - expect: { window: SecurityCameraData, desc: 点"查看历史图像"打开历史报警记录窗体 }
@@ -17,7 +17,7 @@
   steps:
     - clock: '09:00:00'
     - click: pic_security
-    - expect: { control: pic_video, image: true, within: 3s }
+    - expect: { control: pic_video, image: true }
     - click: btn_camera
     - clock: '10:30:00'
     - click: btn_camera
@@ -34,7 +34,7 @@
   steps:
     - clock: '09:00:00'
     - click: pic_security
-    - expect: { control: pic_video, image: true, within: 3s }
+    - expect: { control: pic_video, image: true }
     - click: btn_camera
     - click: btn_history
     - pick: { control: dateTimePicker1, value: '2024-01-01' }