src/hashbang.sh: Support absent private keys

[KellerFuchs]

This will make things work for users with smartcards and equivalents
... or apparently those running the signup script on a remote machine with SSH agent forwarding. 😅

[KellerFuchs]

@alexlehm Could you try this and confirm it fixes your issue?
The script can be run directly from src/hashbang.sh,
or by fetching static/index.html and using gpg to validate and remove the signature.

[alexlehm]

@KellerFuchs yes, it works now for my setup

[KellerFuchs]

@RyanSquared If you could review/merge/build/push at some point that'd be swell ;3

still hasn't had the spoons to make podman work over Tor, to push images.

[RyanSquared]

I've approved this but I'm unsure of why GitHub isn't happy with it. It is saying the commits are not signed. However, git verify-commit $(git log --format=%H origin/master..HEAD) shows they are all signed.

[daurnimator]

It is saying the commits are not signed. However, git verify-commit $(git log --format=%H origin/master..HEAD) shows they are all signed.

github cares too much about the UID