Add multi-meter energy sender schema with UART0/1/2 mode split

include/data_model.h

@@ -28,6 +28,9 @@ struct MeterData {
   uint32_t ts_utc;
   uint16_t short_id;
   char device_id[16];
+  bool energy_multi;
+  uint8_t energy_meter_count;
+  uint32_t energy_kwh_int[3];
   float energy_total_kwh;
   float phase_power_w[3];
   float total_power_w;