feat: add home manager audio module (pulsemixer)

home/hosts/andromache/default.nix

@@ -11,6 +11,7 @@ in
 {
   imports = [
     ../../modules/ai-tools.nix
+    ../../modules/audio
     ../../modules/cloud
     ../../modules/comms
     ../../modules/desktop/niri

home/hosts/astyanax/default.nix

@@ -11,6 +11,7 @@ in
   imports = [
     ../../modules/lib.nix
     ../../modules/ai-tools.nix
+    ../../modules/audio
     ../../modules/anki.nix
     ../../modules/cloud
     ../../modules/comms

home/modules/audio/default.nix

@@ -0,0 +1,5 @@
+{ pkgs, ... }:
+
+{
+  home.packages = with pkgs; [ pulsemixer ];
+}