Add linting, formatting, and CI

- Add deadnix, nixfmt, and statix to flake inputs
- Add formatter output to flake for nix fmt support
- Add deadnix, nixfmt, statix to Home Manager packages
- Format all nix files with nixfmt
- Add GitHub Actions workflow for CI validation
- Support x86_64-darwin in formatter

modules/hosts/nixos/hetznix02/post-install/default.nix

@@ -1,4 +1,5 @@
-{ config, username, ... }: {
+{ config, username, ... }:
+{
   imports = [
     ../../../../shared/nixos/lets-encrypt.nix
     ./monitoring.nix
@@ -23,4 +24,3 @@
     };
   };
 }
-