Make the mobile version more equal to the desktop version

[goto-bus-stop]

We could start paying more attention to the mobile version by, for example, sticking all the desktop-specific stuff into a desktop/ subfolder instead of treating it as the "main" code and mobile as a secondary part.

Mobile should have at least:

• [ ] Playlist creation
• [ ] Media search
• [x] A better settings layout (just needs some flexbox magic probably)

And more nice to have:

• [ ] Importing (actually pretty important but media search is even more critical)
• [ ] Media editing

When selecting a playlist to add media to, we can use the bottom sheet component instead of the popover list.

Also listing some tweaks from https://github.com/u-wave/web/pull/1686 here for now, should move to its own issue later:

• [ ] The mobile loading screen has icons that look clickable, maybe hide them
• [ ] Use the current videoDisabled style also when nobody is playing (but with different text)