Initial commit: ZNET Temperature Sensor ESP32 firmware

- PlatformIO project for Meshnology ESP32 LoRa V3
- DS18B20 dual sensor support for tank verification
- OLED display for local temperature visibility
- HTTP POST to ZNET Web API
- WiFiManager for easy WiFi configuration
- Offline buffering when network unavailable

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

include/config.h

@@ -0,0 +1,100 @@
+/**
+ * ZNET Temperature Sensor Configuration
+ *
+ * Edit these values for your installation.
+ */
+
+#ifndef CONFIG_H
+#define CONFIG_H
+
+// ============================================================================
+// NETWORK CONFIGURATION
+// ============================================================================
+
+// WiFi credentials (can also be set via WiFiManager portal)
+#define WIFI_SSID ""          // Leave empty to use WiFiManager
+#define WIFI_PASSWORD ""
+
+// ZNET Web API endpoint
+#define ZNET_API_URL "http://192.168.1.100:8000/api/v1/sensors/readings"
+
+// Device identification
+#define DEVICE_ID "tank_gateway_1"
+#define DEVICE_NAME "E-Coat Tank Gateway"
+
+// ============================================================================
+// SENSOR CONFIGURATION
+// ============================================================================
+
+// DS18B20 1-Wire data pin
+#ifndef ONEWIRE_PIN
+#define ONEWIRE_PIN 7
+#endif
+
+// Temperature reading interval (milliseconds)
+#define TEMP_READ_INTERVAL_MS 30000  // 30 seconds
+
+// Number of readings to average for stability
+#define TEMP_AVG_READINGS 3
+
+// Sensor IDs (auto-detected, but can be named)
+#define SENSOR_1_NAME "tank_primary"
+#define SENSOR_2_NAME "tank_secondary"
+
+// Temperature validation range (Fahrenheit)
+#define TEMP_MIN_VALID_F 32.0
+#define TEMP_MAX_VALID_F 150.0
+
+// ============================================================================
+// DISPLAY CONFIGURATION
+// ============================================================================
+
+// OLED I2C address
+#define OLED_ADDRESS 0x3C
+
+// Display update interval (milliseconds)
+#define DISPLAY_UPDATE_INTERVAL_MS 1000
+
+// ============================================================================
+// LORA CONFIGURATION (for future remote sensor nodes)
+// ============================================================================
+
+// LoRa frequency (915 MHz for US)
+#define LORA_FREQUENCY 915.0
+
+// LoRa bandwidth (125 kHz)
+#define LORA_BANDWIDTH 125.0
+
+// LoRa spreading factor (7-12, higher = longer range but slower)
+#define LORA_SPREADING_FACTOR 9
+
+// LoRa coding rate (5-8)
+#define LORA_CODING_RATE 7
+
+// LoRa sync word (private network)
+#define LORA_SYNC_WORD 0x12
+
+// ============================================================================
+// API RETRY CONFIGURATION
+// ============================================================================
+
+// Maximum retries for API calls
+#define API_MAX_RETRIES 3
+
+// Retry delay (milliseconds)
+#define API_RETRY_DELAY_MS 5000
+
+// HTTP timeout (milliseconds)
+#define HTTP_TIMEOUT_MS 10000
+
+// ============================================================================
+// BUFFER CONFIGURATION (for offline operation)
+// ============================================================================
+
+// Maximum readings to buffer when offline
+#define OFFLINE_BUFFER_SIZE 100
+
+// Save buffer to flash on reboot
+#define BUFFER_PERSIST_TO_FLASH true
+
+#endif // CONFIG_H