feat: add moonshine_NRF52_ebyte variant (Ebyte nRF52840 + E22-400M33S)

DIY Meshtastic node using an Ebyte nRF52840 MCU module with LFXO crystal
and E22-400M33S LoRa module (SX1268, 433MHz, 33dBm).

Pin assignments:
- LED (LED_PAIRING): P0.15, LED_LORA DIO1: P1.10, BUSY: P0.28 (AIN4)
- LORA_CS: P0.17, RESET: P1.13, RXEN: P1.09, SPI: P0.20/P0.22/P1.00
- VBAT_ADC: P0.03 (0.5 divider), CHAG_DET: P0.13, BUZZER: P1.11
- BUTTON: P0.24, I2C: SDA=P0.08/SCL=P0.04 (wired, no devices)

PA parameters derived from E22-M UserManual V1.2 power curve (not from
E22-900M33S which uses a different PA with 25dB gain):
- SX126X_MAX_POWER=21, TX_GAIN_LORA=12 (chip 21dBm -> module ~33.5dBm)
- DIO2_AS_RF_SWITCH with MCU-controlled RXEN, TCXO 1.8V (TCXO_OPTIONAL)

USB CDC serial enabled by default (nRF52840 built-in). No GPS/screen/
I2C devices. Uses S140 v6 SoftDevice (matches nice!nano bootloader).
Flashable via USB (1200bps touch DFU) or UF2 drag-and-drop.

variants/nrf52840/diy/moonshine_NRF52_ebyte/variant.cpp

@@ -0,0 +1,64 @@
+/*
+  Copyright (c) 2014-2015 Arduino LLC.  All right reserved.
+  Copyright (c) 2016 Sandeep Mistry All right reserved.
+  Copyright (c) 2018, Adafruit Industries (adafruit.com)
+
+  This library is free software; you can redistribute it and/or
+  modify it under the terms of the GNU Lesser General Public
+  License as published by the Free Software Foundation; either
+  version 2.1 of the License, or (at your option) any later version.
+
+  This library is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+  See the GNU Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public
+  License along with this library; if not, write to the Free Software
+  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+*/
+
+#include "variant.h"
+#include "nrf.h"
+#include "wiring_constants.h"
+#include "wiring_digital.h"
+
+const uint32_t g_ADigitalPinMap[] = {
+    // P0
+    0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,
+
+    // P1
+    32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47};
+
+void initVariant()
+{
+    // Configure P0.18 as RESET pin (UICR->PSELRESET).
+    // nrf52_recover (ERASEALL) clears UICR to 0xFFFFFFFF, disabling reset.
+    // SystemInit() already handles this via CONFIG_GPIO_AS_PINRESET; this is a
+    // safety net that runs before SoftDevice is enabled, so NVMC is accessible.
+    if ((NRF_UICR->PSELRESET[0] != 18) || (NRF_UICR->PSELRESET[1] != 18)) {
+        NRF_NVMC->CONFIG = NVMC_CONFIG_WEN_Wen << NVMC_CONFIG_WEN_Pos;
+        while (NRF_NVMC->READY == NVMC_READY_READY_Busy) {}
+        NRF_UICR->PSELRESET[0] = 18;
+        while (NRF_NVMC->READY == NVMC_READY_READY_Busy) {}
+        NRF_UICR->PSELRESET[1] = 18;
+        while (NRF_NVMC->READY == NVMC_READY_READY_Busy) {}
+        NRF_NVMC->CONFIG = NVMC_CONFIG_WEN_Ren << NVMC_CONFIG_WEN_Pos;
+        while (NRF_NVMC->READY == NVMC_READY_READY_Busy) {}
+        NVIC_SystemReset(); // Reboot to apply PSELRESET (hardware reconfigures P0.18)
+    }
+
+    // Initialize pairing LED pin (StatusLEDModule only calls digitalWrite, not pinMode)
+    pinMode(LED_PAIRING, OUTPUT);
+    digitalWrite(LED_PAIRING, LED_STATE_ON ^ 1); // OFF
+}
+
+void variant_shutdown()
+{
+    // Turn off pairing LED
+    nrf_gpio_pin_write(LED_PAIRING, LED_STATE_ON ^ 1);
+
+    nrf_gpio_cfg_input(BUTTON_PIN, NRF_GPIO_PIN_PULLUP); // Enable internal pull-up on the button pin
+    nrf_gpio_pin_sense_t sense = NRF_GPIO_PIN_SENSE_LOW; // Configure SENSE signal on low edge
+    nrf_gpio_cfg_sense_set(BUTTON_PIN, sense);           // Apply SENSE to wake up the device from the deep sleep
+}