Redesign 2024 + Adaptiveness & Darkmode support

As promised, I started on working on top of !264 (closed). (A few days later than promised, though.)

It is by no means finished. The things I still want to do include

• needs a box for the user interface logos – they don't work on plain dark background
• hover state was adjusted in some places, but not yet all of them
• inline SVGs for icons would be great to remove the extra network requests, and allow for fill instead of the hacky filter
• fonts need to be changed per comments on the previous iteration of this MR
• remove hard-coded font sizes in favour of them relative to rem
• mention somewhere in the footer: design by dikasp (@dikasetyaprayogi), @camelCaseNick (or however you want to add credit for yourself) and @ollieparanoid

But I open it now, to get out the things I started on, especially, the dark mode, where the one pmOS green is split into two. Do you think this works?

Close #169 (closed)