disko module defines options under `disko.devices.disk.*`, not
`disk.*`. This was causing evaluation error:
"The option 'disk' does not exist. Did you mean 'disko'?"
- Add disko flake input + partition config (/boot/firmware, /, /home)
- Add cm5-backlight-fix service as display fallback
- Add enable-gpio23-usb-hub service for internal USB hub
- Add mt7921u kernel module for MediaTek AC1200 WiFi
- Add gpiod package for GPIO userspace control