dashborad实时监控的数据时间支持配置化，不再hard code

dashboard实时监控的时间跨度在代码中hard code了，是否可以搞成配置化，可以让用户进行配置。


The issue names only the dashboard’s real-time monitoring time span and provides screenshots; no file or test is specified. Start by locating the dashboard monitoring entry point and the existing hard-coded span, then trace the available configuration mechanisms. Done means users can configure the span and the dashboard uses that value instead of a hard-coded one.

Written by the indexing model from the issue text.