chore: move firmware out of main tree

flake.nix

@@ -54,6 +54,11 @@
       inputs.nixpkgs.follows = "nixpkgs";
     };
 
+    apple-firmware = {
+      url = "git+https://code.youwen.dev/youwen5/apple-firmware";
+      flake = false;
+    };
+
     spicetify = {
       url = "github:Gerg-L/spicetify-nix";
       inputs.nixpkgs.follows = "nixpkgs";

hosts/callisto/configuration.nix

@@ -18,7 +18,7 @@
   boot.loader.efi.canTouchEfiVariables = false;
 
   hardware.asahi = {
-    peripheralFirmwareDirectory = ./firmware;
+    peripheralFirmwareDirectory = "${inputs.apple-firmware}/firmware"
     useExperimentalGPUDriver = true;
     experimentalGPUInstallMode = "overlay";
   };