Adapt to system light/dark mode instantly without requiring refresh

[bragefuglseth]

Initial Checklist

• I understand this is a feature request and questions should be posted in the Community Discussions
• I searched issues and couldn’t find anything (or linked relevant results below)

Idea

When I switch my system from light to dark mode or vice versa, the web UI currently requires a refresh before the change is reflected.

A lot of contemporary websites (for instance GitHub) do this nice thing where they switch on the fly, either using the prefers-color-scheme CSS media feature, or programatically with matchMedia() and an event listener.

Could the OpenCloud web UI do the same when the theme is set to follow the system?