Automate the scriptable parts of the OOBA checklist

[eliasbakken]

The OOBA (Out-Of-Box-Audit) checklist in README.md is entirely manual today:

• Wifi comes up as an AP/Station
• Webcam shows a picture
• USB host/device works as expected
• Default Klipper config does not have any errors
• All systemd services are running as they should
• Software updates look functional
• Shaper calibrate works
• A print can be performed
• The LEDs are working
• KlipperScreen works and can be used to control the printer

A chunk of this can be scripted (e.g. scripts/validate-image.sh, run over SSH against a freshly flashed board), shrinking the manual list down to just what genuinely needs a human.

Fully scriptable:

• All systemd services are running as they should — systemctl is-active against the expected service list
• Default Klipper config does not have any errors — query Moonraker's /printer/info for state: ready, grep klippy.log for absence of Error/Shutdown/Traceback
• Software updates look functional — query Moonraker's update_manager status API, assert no errors per tracked repo

Partially scriptable (can verify the pipeline works end-to-end, not that the result looks right to a human):

• Webcam shows a picture — check the streamer service is active, curl the snapshot endpoint, assert HTTP 200 + valid JPEG + non-trivial size
• Wifi comes up as an AP/Station — check via nmcli/iw which connection is actually active (ties into The Wifi hotspot/Client priority is not repected #65)
• USB host/device works as expected — check gadget/configfs state and controller role
• The LEDs are working — confirm a LED gcode command completes without error

Needs a human, not realistically scriptable:

• Shaper calibrate works
• A print can be performed
• KlipperScreen works and can be used to control the printer

Plan: start with the fully-scriptable tier, build outward from there.