Replace client router

[maxlath]

As our Backbone/Marionette code is getting closer to extinction, there will come a day were the last piece of Backbone will be the router. We haven't had to complain much about it, but we might find reasons to look into more recent alternatives.

Here is a link dump of things to watch in that space:

• storing a layout's state as query strings in the URL: we already do that in some cases, but we could do way more, and it would be useful to have a nice primitive for that purpose.
  • sveltekit-search-params
  • skRoutes
  • TanStack/router (React) could be a source of inspiration.