The system-wide SSH server was hidden behind a wireguard proxy for
security reasons, but since forgejo was using it, git pushes and pulls
got broken for people without wireguard access.
These config changes make sure forgejo starts its built-in SSH server
on port 22, which is then allowed to be accessed from the open internet
in the firewall config.
This commit changes the file structure around, so that we have the
following parts:
`/modules` contains reusable logic blocks for hosts.
`/hosts` contains host configurations.
`/lib` contains nix library functions.
`/overlays` contains overlay files.
`/public-keys` contains all information regarding public keys.
This change reduces the complexity of flake.nix, instead delegating this
out to the `default.nix` files in the above directories.
