feat(nix): add sound configuration for PipeWire priorities

- Introduced `sound.nix` to manage audio device priorities using PipeWire's WirePlumber configuration.
- Linked `sound.nix` to `default.nix` for streamlined system audio customization.
- Ensures defined priority levels for HDMI, USB microphones, and SPDIF outputs.

systems/x86_64-linux/amd/sound.nix

@@ -0,0 +1,40 @@
+{ ... }:
+{
+  services.pipewire.wireplumber.extraConfig."51-audio-priorities" = {
+    "monitor.alsa.rules" = [
+      {
+        matches = [
+          { "node.name" = "alsa_output.pci-0000_73_00.1.hdmi-stereo"; }
+        ];
+        actions = {
+          update-props = {
+            "priority.session" = 2000;
+            "priority.driver" = 2000;
+          };
+        };
+      }
+      {
+        matches = [
+          { "node.name" = "alsa_output.usb-R__DE_Microphones_R__DE_NT-USB_Mini_6893EA23-00.analog-stereo"; }
+        ];
+        actions = {
+          update-props = {
+            "priority.session" = 1500;
+            "priority.driver" = 1500;
+          };
+        };
+      }
+      {
+        matches = [
+          { "node.name" = "alsa_output.usb-Generic_USB_Audio-00.HiFi__SPDIF__sink"; }
+        ];
+        actions = {
+          update-props = {
+            "priority.session" = 1000;
+            "priority.driver" = 1000;
+          };
+        };
+      }
+    ];
+  };
+}