[WIP] Update + clean up dependencies, move API crates into repo, s/Docker/Nix

[rcoder]

This does a number of things which could be separated, so I consider this more or less experimental.

Implied in the removal of the various dockerfiles is the expectation that production deployments of ZeroNSD will simply use a Docker container, rather than distro-native packages.

TODO: automate publishing of containers from Nix-generated image