refactor: extract host config into 'host.nix' files

hosts/vm/default.nix

@@ -12,6 +12,7 @@
     ./hard.nix
     inputs.sops-nix.nixosModules.sops
     ./disk.nix
+    ./host.nix
     ../../modules/boot/bootloader.nix
     ../../modules/keyboard
     (import ../../modules/networking { hostName = config.host.name; })
@@ -27,11 +28,6 @@
     })
   ];
 
-  host = {
-    username = "h";
-    name = "vm";
-  };
-
   home-manager.users.${config.host.username} = import ../../home/hosts/vm {
     inherit inputs config pkgs;
   };