Add Arduino support, dialout group, and Zed skill

- Enable the Arduino IDE flatpak and add it to the system modules list.

- Add the user to the `dialout` group for serial device access.
- Include a new Zed skill configuration that fetches a remote skill
  file.

modules/core/flatpak.nix

@@ -15,6 +15,7 @@
     warehouse = "io.github.flattool.Warehouse";
     flatseal = "com.github.tchx84.Flatseal";
     upscaler = "io.gitlab.theevilskeleton.Upscaler";
+    arduino = "cc.arduino.IDE2";
   };
 in {
   options.flatpak.enable = lib.mkEnableOption "Flatpak";

modules/core/user.nix

@@ -66,6 +66,7 @@
         "vboxusers" # Virtual Box
         "gamemode"
         "lpadmin"
+        "dialout"
       ];
       shell = with pkgs; (
         if shell == "fish"