What this PR does / why we need it?

修复子网站在“停止后再启动”场景下无法恢复访问的问题。子网站被停止后会命中停站页，但再次启动时未正确恢复对应 Nginx 配置，导致持续显示停站提示。 #11669

Summary of your change

在网站启动逻辑中补充 subsite 分支处理，按父站点类型恢复子网站 root 与代理配置，父站点为 PHP 运行时时恢复对应 PHP 转发配置，同步必要运行字段，确保状态与配置一致。

Please indicate you've done the following:

• Made sure tests are passing and test coverage is added if needed.
• Made sure commit message follow the rule of Conventional Commits specification.
• Considered the docs impact and opened a new docs issue or PR with docs changes if needed.