Add LoRa sensor network support

- Design LoRa packet protocol with CRC16 validation
- Add protocol header files (lora_protocol.h, lora_packet.h)
- Create battery-powered remote node firmware template
  - Support for DHT22, BME680, DS18B20 sensors
  - Deep sleep for battery conservation
  - Automatic gateway registration
- Add LoRa receive to gateway firmware
  - RadioLib SX1262 integration
  - Node registry for tracking up to 16 nodes
  - HTTP forwarding of received readings
  - ACK responses to remote nodes
- Create comprehensive setup guide with wiring diagrams

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

remote-node/include/config.h

@@ -0,0 +1,154 @@
+/**
+ * ZNET LoRa Remote Sensor Node Configuration
+ *
+ * Edit these values for your specific node deployment.
+ */
+
+#ifndef CONFIG_H
+#define CONFIG_H
+
+// ============================================================================
+// NODE IDENTIFICATION
+// ============================================================================
+
+// Unique node ID (see docs/LORA_PROTOCOL.md for ID ranges)
+// - 0x0100-0x01FF: Ambient sensors (DHT22)
+// - 0x0200-0x02FF: Environmental (BME680)
+// - 0xFFFF: Request auto-assignment from gateway
+#ifndef NODE_ID
+#define NODE_ID 0xFFFF  // Auto-assign
+#endif
+
+// Human-readable node name (max 8 chars)
+#ifndef NODE_NAME
+#define NODE_NAME "Remote1"
+#endif
+
+// Firmware version
+#define FW_VERSION_MAJOR 1
+#define FW_VERSION_MINOR 0
+
+// ============================================================================
+// SENSOR CONFIGURATION
+// ============================================================================
+
+// Sensor type is set by platformio.ini build flags:
+// -DSENSOR_TYPE_DHT22  or  -DSENSOR_TYPE_BME680
+
+// DHT22 data pin (if not set by build flags)
+#ifndef DHT_PIN
+#define DHT_PIN 7
+#endif
+
+// BME680 I2C address (0x76 or 0x77)
+#ifndef BME680_I2C_ADDR
+#define BME680_I2C_ADDR 0x76
+#endif
+
+// DS18B20 1-Wire pin (if using DS18B20 variant)
+#ifndef ONEWIRE_PIN
+#define ONEWIRE_PIN 7
+#endif
+
+// ============================================================================
+// TIMING CONFIGURATION
+// ============================================================================
+
+// Report interval in seconds (default: 60 sec)
+// Can be overridden by gateway via CONFIG_RESP packet
+#ifndef REPORT_INTERVAL_SEC
+#define REPORT_INTERVAL_SEC 60
+#endif
+
+// How long to wait for ACK (milliseconds)
+#define ACK_TIMEOUT_MS 3000
+
+// Maximum retries if no ACK received
+#define MAX_RETRIES 3
+
+// How long to listen for incoming packets after TX (milliseconds)
+#define RX_WINDOW_MS 500
+
+// ============================================================================
+// LORA CONFIGURATION
+// ============================================================================
+
+// Frequency (US: 915 MHz, EU: 868 MHz, AS: 923 MHz)
+#ifndef LORA_FREQUENCY
+#define LORA_FREQUENCY 915.0
+#endif
+
+// Spreading factor (7-12, higher = longer range, slower)
+#define LORA_SPREADING_FACTOR 9
+
+// Bandwidth (kHz)
+#define LORA_BANDWIDTH 125E3
+
+// Coding rate (5-8)
+#define LORA_CODING_RATE 7
+
+// Sync word (must match gateway: 0x12)
+#define LORA_SYNC_WORD 0x12
+
+// TX power (dBm, max 20 for US)
+#define LORA_TX_POWER 14
+
+// ============================================================================
+// BATTERY MONITORING
+// ============================================================================
+
+// Battery voltage thresholds (millivolts)
+#define BATTERY_FULL_MV     4200  // Fully charged LiPo
+#define BATTERY_NOMINAL_MV  3700  // Nominal LiPo
+#define BATTERY_LOW_MV      3400  // Low battery warning threshold
+#define BATTERY_CRITICAL_MV 3200  // Critical - send alert
+
+// ADC calibration
+// Voltage divider ratio (if using voltage divider for ADC)
+// Set to 1.0 if reading directly (not recommended for LiPo)
+#define BATTERY_DIVIDER_RATIO 2.0
+
+// ============================================================================
+// ALERT THRESHOLDS (can be overridden by gateway)
+// ============================================================================
+
+// Temperature thresholds (Celsius)
+#define ALERT_TEMP_HIGH_C     35.0   // Too hot
+#define ALERT_TEMP_LOW_C      10.0   // Too cold
+
+// Humidity thresholds (percent)
+#define ALERT_HUMIDITY_HIGH   85.0   // Too humid
+#define ALERT_HUMIDITY_LOW    20.0   // Too dry
+
+// IAQ threshold (BME680 only)
+#define ALERT_IAQ_THRESHOLD   150    // Unhealthy air
+
+// Duration before alert is sent (seconds)
+#define ALERT_PERSIST_SEC     30
+
+// ============================================================================
+// DEEP SLEEP CONFIGURATION
+// ============================================================================
+
+// Use deep sleep between readings (recommended for battery)
+#define ENABLE_DEEP_SLEEP 1
+
+// Wake up sources
+#define WAKE_ON_TIMER 1     // Wake on interval timer
+#define WAKE_ON_GPIO  0     // Wake on external GPIO (for alerts)
+#define WAKE_GPIO_PIN 0     // GPIO pin for external wake
+
+// ============================================================================
+// DEBUG CONFIGURATION
+// ============================================================================
+
+// Enable serial debug output (disable in production to save power)
+#define ENABLE_SERIAL_DEBUG 1
+
+// Enable OLED display (disable to save power if not needed)
+#define ENABLE_OLED 1
+
+// Blink LED on TX (for debugging)
+#define ENABLE_TX_LED 1
+
+#endif // CONFIG_H