refactor(hardware): reorganize module structure

modules/nixos/hardware/audio.nix

@@ -0,0 +1,13 @@
+{
+  flake.modules.nixos.hardware = {
+    security.rtkit.enable = true;
+
+    services.pipewire = {
+      enable = true;
+      alsa.enable = true;
+      alsa.support32Bit = true;
+      pulse.enable = true;
+      wireplumber.enable = true;
+    };
+  };
+}