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.

hosts/default/system-modules.nix

@@ -11,6 +11,7 @@ _: {
       warehouse.enable = false; # Flatpak manager
       flatseal.enable = false; # Flatpak permissions manager
       upscaler.enable = false; # Upscaler: Upscale and enhance images
+      arduino.enable = false; # Arduino: Open-source electronics prototyping platform
     };
   };