Login buttons still exist when already logged in

[DrewMcArthur]

I'd expect to only see the "sign out" button once I've logged in.

i'll open a PR that fixes this shortly, this seems like a good introduction to the codebase :)

great project, thanks for your work on it!

[K-Nksm]

The reasoning is detailed in https://github.com/whtwnd/whitewind-blog/pull/15#issuecomment-2424003125