Support RockBase IoT NM-EPD-420-4C with EP42YR_400x300 panel

[RockBase-iot]

Adds full device support for the NM-EPD-420-4C:

• Reuses the esp32-s3-N16R8 environment with 400×300 B/W/R/Y full-refresh support.
• Adds panel mapping, GPIO, button, battery, and deep-sleep wake configuration.
• Supports wake-time temperature and humidity sampling via AHT20.
• Adds low-power peripheral initialization, device configuration, preset data, and a factory firmware image.
• Partial refresh remains disabled for the four-color panel.

Verified on hardware: display refresh, physical buttons, BOOT wake, and battery reporting.

Tested with Home Assistant. The AHT20 need change the sensor.py to support sensor_type = 7 for AHT20.

[jonasniesner]

Thank you for your PR. Instead of creating the devices files, please open a pr against the website repo. And and the .md file is not required. Once you address this, I will re review your PR and if it passes, merge it

[RockBase-iot]

Thanks for the feedback! I've addressed both points:

• Removed the device files from this PR — devices/nm-epd-420-4c.yaml, devices/nm-epd-420.simple-config-preset.json, and docs/DEVICE_NM_EPD_420_4C.md are all gone. The PR now contains only the firmware code changes (panel mapping, NM420 init flag, AHT20 sensor support, and the od-device-cli.py enum update).

• Opened a PR against the website repo with the driver board preset: Add RockBase IoT NM-EPD-420 (ESP32-S3) driver board preset opendisplay.org#165 — it adds the nm-epd-420-4c entry (driverBoards index 32) to simple-config-presets.json, pointing at the existing ep42yr-400x300 display preset and battery-650 power option, plus the matching simple-config-id-registry.json entry. Validated locally with .github/scripts/validate-simple-config-presets.py (simple-config OK: 89 presets; id/index registry stable).

Ready for re-review. Let me know if anything else needs adjusting.