ci: Build and publish latest (nightly) binaries - #308

Goreleaser natively supports nightly builds and uses them itself: https://github.com/goreleaser/goreleaser/releases/tag/nightly
I did brief research recently, please see: https://claude.ai/share/80618728-c1b8-47ec-8476-087b78715169

So if we use goreleaser for all current releases, let's try using it for nightly as well.

Ah, it requires Pro which is a subscription, not a one-time payment hmmm. That's a bummer. I'm also interested if there a way to script/emulate such a behaviour using a regular release process.

A relevant comment from discord:

Sounds like we probably need to invest some time in configuring the nightly build infrastructure so there is always builds with the latest changes are available. Combining this with uc machine init/add --version nightly and a command to upgrade daemons #142 sounds like a great way to test latest changes/fixes.

Switched to using goreleaser (also added it to Mise); renamed to nightly.

uc machine init/add --version nightly should work now, but will test properly when we have the release in place.