chore: flake update + optimizations

overlays/default.nix

@@ -3,7 +3,7 @@
   additions = final: prev:
     (import ../pkgs {pkgs = final;})
     // {
-      zugferd-service = inputs.zugferd-service.packages.${prev.system}.default;
+      zugferd-service = inputs.zugferd-service.packages.${prev.stdenv.hostPlatform.system}.default;
     };
 
   # This one contains whatever you want to overlay
@@ -21,13 +21,13 @@
 
   stable-packages = final: _prev: {
     stable = import inputs.nixpkgs {
-      system = final.system;
+      system = final.stdenv.hostPlatform.system;
       config.allowUnfree = true;
     };
   };
   unstable-packages = final: _prev: {
     unstable = import inputs.nixpkgs-unstable {
-      system = final.system;
+      system = final.stdenv.hostPlatform.system;
       config.allowUnfree = true;
     };
   };