CMS: Dark mode

[MrDirkelz]

My browser set my dark mode for the cms automatically. Think this actually looks like a nice dark mode for the cms. But can obviously improved by the one that works on it.

[ivanslabbert]

implement the same dark mode colour scheme that we use in the app.
At first we can just use the browsers dark / light mode preference (from OS preference), and when that is working we can add user preferences like in the app.

[brucefrankstad26-beep]