Initial project: XIAO ESP32S3 + SX1262 LoRa sensor link hytte–hjem

- cabin_node: subscribes to local MQTT (ESPHome sensors), sends
  temperature, battery voltage/SOC and switch states over LoRa SF12
- cabin_gw: receives LoRa packets, publishes JSON to home MQTT broker
- Bidirectional: gateway forwards ON/OFF commands from home HA to node
- cabin_node always in RX mode (12V powered) — commands arrive instantly
- ESPHome config for ESP32 on teknisk rom: Victron MPPT BLE + JBD BMS
  BLE + DS18B20 temperatures + GPIO switches for varme/VVB

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

platformio.ini

@@ -0,0 +1,26 @@
+[platformio]
+default_envs = cabin_node
+
+[env:cabin_node]
+platform = espressif32
+board = seeed_xiao_esp32s3
+framework = arduino
+build_src_filter = +<cabin_node/> -<cabin_gw/>
+build_flags = -I include
+monitor_speed = 115200
+lib_deps =
+  jgromes/RadioLib@^7.1.2
+  knolleary/PubSubClient@^2.8
+  bblanchon/ArduinoJson@^7.0.4
+
+[env:cabin_gw]
+platform = espressif32
+board = seeed_xiao_esp32s3
+framework = arduino
+build_src_filter = +<cabin_gw/> -<cabin_node/>
+build_flags = -I include
+monitor_speed = 115200
+lib_deps =
+  jgromes/RadioLib@^7.1.2
+  knolleary/PubSubClient@^2.8
+  bblanchon/ArduinoJson@^7.0.4