chore(清理): 删掉并行试跑、搬库、Python3 别名、旧链接这些过渡期的兼容写法

- 部署：JUDGE_STATE_DIR 不再强制设；删掉搬库脚本和只为搬库存在的自检、提醒
- 语言：Python3 / Python2 别名表删掉，normalizeLanguage 改名 parseLanguage
- 旧链接：后台题单详情的跳转、用户列表 -last_login 的转换
- 旧页面：布置作业必须带 language（null = 没选）；不再清旧版出题页草稿

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

docker/compose.school.yml

@@ -48,7 +48,7 @@ services:
       - /tmp
     volumes:
       - ${DATA_DIR:-../data}/backend/test_case:/test_case:ro
-      # 并行试跑时必须单独设 JUDGE_STATE_DIR，否则新旧两个 judger 共用一个运行目录
+      # 判题机的运行状态目录，默认跟着 DATA_DIR 走
       - ${JUDGE_STATE_DIR:-${DATA_DIR:-../data}/judge_server}/log:/log
       - ${JUDGE_STATE_DIR:-${DATA_DIR:-../data}/judge_server}/run:/judger
     environment:
@@ -121,6 +121,5 @@ services:
     volumes:
       - ${DATA_DIR:-../data}/backend/log:/data/log
     ports:
-      # 并行试跑时换一个端口，81 还被旧 backend 占着
       - "${WEB_PORT:-81}:8000"
     mem_limit: 256m