Remote deployment: allow local builds

[srid]

When using small VPS, it doesn't make sense to build everything remotely. For this, provide an option to so we can build everything locally and nix copy it before doing remote deployment.

For now, we must do this manually, e.g.:

nix copy $(nix build .\#nixosConfigurations.naivete-me.config.system.build.toplevel --no-link --print-out-paths)  --to ssh-ng://root@<ip>q

[srid]

Workaround in the meanwhile:

https://github.com/srid/naivete-me/blob/2f5321e6bd30afd1d9e0f2e5a1bd7c486d358a83/justfile#L23-L29