refactor: Make hw definitions modules with mkIf guards

fleet/default.nix

@@ -20,8 +20,6 @@ let
   # Import fleet-option.nix (defines athenix.fleet) and inventory.nix (sets values)
   # We use a minimal module here to avoid circular dependencies from common.nix's imports
 
-  hostTypes = config.athenix.hwTypes;
-
   # Helper to create a single NixOS system configuration
   mkHost =
     {
@@ -123,11 +121,6 @@ let
         }
       ) userNixosModulePaths;
 
-      # Get the host type module from the hostTypes attribute set
-      typeModule =
-        hostTypes.${hostType}
-          or (throw "Host type '${hostType}' not found. Available types: ${lib.concatStringsSep ", " (lib.attrNames hostTypes)}");
-
       # External module from fetchGit/fetchurl
       externalPathModule =
         if externalModulePath != null then import externalModulePath { inherit inputs; } else { };
@@ -155,18 +148,24 @@ let
           ];
         };
 
+      # Hardware-specific external modules
+      hwSpecificModules =
+        lib.optional (hostType == "nix-lxc") "${inputs.nixpkgs.legacyPackages.${system}.path}/nixos/modules/virtualisation/proxmox-lxc.nix";
+
       allModules =
         userNixosModules
         ++ [
           ./common.nix
-          typeModule
           overrideModule
           { networking.hostName = hostName; }
           {
             # Inject user definitions from flake-parts level
             config.athenix.users = lib.mapAttrs (_: user: lib.mapAttrs (_: lib.mkDefault) user) users;
           }
+          # Enable the appropriate hardware module based on hostType
+          { config.athenix.hw.${hostType}.enable = lib.mkDefault true; }
         ]
+        ++ hwSpecificModules
         ++ lib.optional (externalModulePath != null) externalPathModule;
     in
     {