optiscaler: package v0.9.1

stdenvNoCC + p7zip extraction; strips installer scripts and README,
keeps Licenses/. dontFixup since the artifacts are Windows DLLs.
meta.license is unfreeRedistributable to reflect the bundled XeSS
(Intel SLA) alongside the GPL-3.0 source.

Wires lib/overlays.nix into mkDesktopHost (was muffin-only) and adds
"optiscaler" to the unfree allowlist on jovian hosts so yarn can
consume it without flipping the global allowUnfree flag.

flake.nix

@@ -237,6 +237,7 @@
                 home-manager.users.${username} = import ./hosts/${hostname}/home.nix;
               }
             )
+            { nixpkgs.overlays = [ (import ./lib/overlays.nix) ]; }
             ./hosts/${hostname}/default.nix
           ];
         };