feat: Disable /preview for unpublished flows

[DafyddLlyr]

Context

Quick proof of concept to follow up on discussion point from yesterday about publishing flows. No strong feelings about when / how this proceeds - it might make sense to bundle a bunch of related "publish" changes together such as #2783?

What does this PR do?

• Disable "preview" icon in Editor if flow is unpublished
• Throws a NotFound error on /preview routes for unpublished flows (no fallback to dataMerged() / "unpublished" version of the flow)
  • If we go ahead with this it's probably worth improving this - not found for public, a meaningful message for logged in Editors maybe?
• A few type tidy ups 🧹

[github-actions]

🤖 Hasura Change Summary compared a subset of table metadata including permissions:

Updated Tables (2)

• public.flows permissions:

  	insert	select	update	delete
  api		➕/➖
  platformAdmin		➕/➖
  public		➕/➖
  teamEditor		➕/➖

• public.published_flows permissions:

  	insert	select	update	delete
  api		➕/➖
  platformAdmin		➕/➖
  public		➕/➖
  teamEditor		➕/➖

[github-actions]

Removed vultr server and associated DNS entries

[jessicamcinchak]

Works as expected for me!

Asked a UI coordination question in Slack very similar to what you've anticipated here - no strong feelings either way, but worth noting that I'm working on re-locating dataMerged to planx-core so would be nice to merge this/rebase mine sooner than later to avoid merge conflicts 👌