feat: Route loading progress bar

[DafyddLlyr]

An implementation of a routing loading bar as opposed to the FOUC and DelayedLoadingIndicator.

Follows on from #3671

Questions -

• Is 50ms of delay too short? (is it showing too often and flashing and dissapearing?)
• Style
  • should it be slimmer?
  • should it be a more subtle colour
• Do we want to consider something similar on the public interface?

[github-actions[bot]]

Removed vultr server and associated DNS entries

[DafyddLlyr]

Thanks @jessicamcinchak 🙌

Keen to progress this and draw a line so I'll mere both PRs to main - confident enough it's a solid improvement even if not visually perfect. I'll then flag at standup and in #planx-design just to make sure a design eye is cast over it 👍