[Feature Request]: the responsive design of the bar

**Is your feature request related to a problem? Please describe.**
when the sidebar show or hide, the bar(look at the pictures) does not expand , i think this is ugly

**Describe the solution you'd like**
when the sidebar hide, the bar should expand

**Describe alternatives you've considered**

**Additional context**

Look at the frontend components for the sidebar and the bar (likely in HTML/CSS or a templating system). The issue shows screenshots of the bar not expanding when the sidebar hides. Find the CSS or JavaScript that controls the bar's width and sidebar visibility. Test by toggling the sidebar and observing the bar's behavior.

索引モデルが issue の本文から書いたものです。