feat(home): add RetroArch for device "ryu" and update MPV config

Add RetroArch as a home package for devices named "ryu" and enhance MPV configuration with GPU settings. Adjust wallpaper engine service to improve performance. Add a script for enabling HDR with Steam commands.

home/programs/retroarch.nix

@@ -0,0 +1,8 @@
+{
+  pkgs,
+  device,
+  lib,
+  ...
+}: {
+  home.packages = lib.optionals (device.name == "ryu") [pkgs.retroarch-full];
+}