Add Raspberry Pi Pico / Pico W + Dragino SX1276 variants

[LegoManACM]

Adds board variants for a Raspberry Pi Pico or Pico W wired to a Dragino LoRa shield (SX1276, PA_BOOST output), a cheap, easy-to-find combination for building a MeshCore node by hand.

Wiring (SPI0)

Signal	Pico GPIO
SCK	18
MOSI	19
MISO	16
NSS	17
DIO0	6
DIO1	7
RESET	8
GPS TX / RX (optional, UART0)	12 / 13

Envs

Variant	Envs
pico_dragino_sx1276 (Pico)	pico_dragino_repeater, pico_dragino_room_server, pico_dragino_companion_radio_usb
pico_w_dragino_sx1276 (Pico W)	the same three as pico_w_dragino_*, plus pico_w_dragino_companion_radio_ble

Notes

• Board class: PicoDraginoBoard is a thin subclass of WaveshareBoard (from waveshare_rp2040_lora). It reports its own manufacturer name and no battery voltage, because this wiring has no battery sense divider.
• Radio: LORA_TX_POWER=20 and SX127X_CURRENT_LIMIT=240. Frequency, bandwidth and SF come from the global defaults, like the other variants.
• Bluetooth: the BLE env uses the existing helpers/rp2040/SerialBLEInterface.

Also included: RP2040 GPS fix

EnvironmentSensorManager::initBasicGPS() calls Serial1.setPins(), which arduino-pico's SerialUART doesn't have (its equivalent is setPinout(tx, rx)). As a result, ENV_INCLUDE_GPS=1 doesn't compile on RP2040. This adds an RP2040_PLATFORM branch. It's a separate commit, so it's easy to drop if you'd rather take it on its own.

Testing

• All 7 envs build with framework-arduinopico 1.60100.0.
• Running on real hardware, from my local branch (same pins and radio setup):
  • Pico W repeater: boots, the SX1276 initialises and receives packets, and GPS is detected.
  • Pico USB companion: works with the MeshCore web app and transmits and receives over LoRa. It ran at 17 dBm. At 20 dBm this particular unit locked up on transmit, which I suspect is a power or cable issue on my bench, since the Pico W is fine at 20.
• Build-only, not hardware-tested: both room servers, pico_dragino_repeater, and the Pico W USB and BLE companions.

🤖 Generated with Claude Code