Rename modules directory system to nixos

flake-parts/modules.nix

@@ -1,7 +1,7 @@
 { self, ... }:
 {
   flake = {
-    nixosModules.default.imports = self.lib.listNixFilesRecursively "${self}/modules/system";
+    nixosModules.default.imports = self.lib.listNixFilesRecursively "${self}/modules/nixos";
     homeModules.default.imports = self.lib.listNixFilesRecursively "${self}/modules/home";
   };
 }