build-clan: move clan attribute relates modules into subfolder

lib/modules/clan/default.nix

@@ -0,0 +1,9 @@
+{clanLib}: {
+  _module.args = {
+    inherit clanLib;
+  };
+  imports = [
+    ./module.nix
+    ./interface.nix
+  ];
+}

lib/modules/default.nix

@@ -9,8 +9,7 @@
 {
   flakePartsModule = {
     imports = [
-      (lib.modules.importApply ./clan/interface.nix { inherit clanLib; })
+      (lib.modules.importApply ./clan/default.nix { inherit clanLib; })
-      ./clan/module.nix
     ];
   };