feat: add RockBase IoT NM-EPD-420 board support

[RockBase-iot]

NM-EPD-420 is an ESP32-S3 based device with:

• 4.2" GDEY042Z98 tri-color EPD (driven B/W/R, 400x300, FSPI)
• SX1262 LoRa transceiver (Heltec RA62, HSPI)
• AHT20 temperature/humidity sensor (I2C, power-gated via GPIO40)
• Battery monitoring (GPIO43 enable, GPIO3 ADC, 2.0x multiplier)
• WS2812 LED (GPIO47), USER button (GPIO45)

Changes:

• boards/nm_epd_420.json: PlatformIO board definition
• variants/esp32s3/nm_epd_420/: variant.h, platformio.ini, nicheGraphics.h, pins_arduino.h for both classic GxEPD2 and InkHUD environments
• src/platform/esp32/architecture.h: add HW_VENDOR mapping for NM_EPD_420
• src/PowerFSM.cpp: skip screensaver for boards with EINK_KEEP_SCREEN_ACTIVE
• src/graphics/EInkDisplay2.cpp/h: 3-color EPD support, NM_EPD_420 rotation
• src/graphics/EInkDynamicDisplay.cpp/h: configurable refresh rate macros
• src/graphics/draw/UIRenderer.cpp: custom dashboard frame for NM_EPD_420
• src/modules/Telemetry/EnvironmentTelemetry.cpp/h: compile-time screen enable
• src/modules/Modules.cpp: load EnvironmentTelemetry when screen enable forced

🤝 Attestations

• I have tested that my proposed changes behave as described.
• I have tested that my proposed changes do not cause any obvious regressions on the following devices:
  • Heltec (Lora32) V3
  • Heltec Vision Master E290
  • LilyGo T-Deck
  • LilyGo T-Beam
  • RAK WisBlock 4631
  • Seeed Studio T-1000E tracker card
  • Other (please specify below)

[github-actions]

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