Explore Clerk keyless mode to make env vars even easier

[jlengstorf]

It looks like supplying no Clerk keys should run Clerk in "keyless mode", which should be just fine for local dev. Need to test this and see how the Astro integration handles it.

[jlengstorf]

I think the Astro plugin from Clerk doesn't support keyless mode. Need to research that a bit. For now,
b3381dc should allow local dev and only causes problems when loading things that explicitly require auth (e.g. the dashboard, the protected Mux player)