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>

server/src/app.ts

@@ -24,7 +24,7 @@ import { languageService } from './language-service'
 import { getReview, gradebook, manualScore, saveReview, studentDetail, submissionFiles } from './reviews'
 import type { GradingQueue } from './grading/queue'
 import { config } from './config'
-import { restoreExperimentDatabases, userDatabaseDir } from './databases'
+import { deleteUserDatabases, restoreExperimentDatabases, userDatabaseDir } from './databases'
 import { listSamples, loadChecks, loadSample } from './samples'
 import { SqlError, sqlService } from './sql-service'
 import { serveStatic } from './static'
@@ -280,8 +280,8 @@ export function createApp(db: Database, gradingQueue: GradingQueue, aiQueue: AiQ
     return password ? c.json({ password }) : c.json({ message: '学生不存在' }, 404)
   })
 
-  app.delete('/api/teacher/students/:id', (c) => {
-    deleteStudent(db, id(c))
+  app.delete('/api/teacher/students/:id', async (c) => {
+    if (deleteStudent(db, id(c))) await deleteUserDatabases(id(c))
     return c.json({})
   })