Add LoRa telemetry, fault counters, and time sync status

include/data_model.h

@@ -2,6 +2,19 @@
 
 #include <Arduino.h>
 
+enum class FaultType : uint8_t {
+  None = 0,
+  MeterRead = 1,
+  Decode = 2,
+  LoraTx = 3
+};
+
+struct FaultCounters {
+  uint32_t meter_read_fail;
+  uint32_t decode_fail;
+  uint32_t lora_tx_fail;
+};
+
 struct MeterData {
   uint32_t ts_utc;
   uint16_t short_id;
@@ -13,6 +26,13 @@ struct MeterData {
   float battery_voltage_v;
   uint8_t battery_percent;
   bool valid;
+  int16_t link_rssi_dbm;
+  float link_snr_db;
+  bool link_valid;
+  uint32_t err_meter_read;
+  uint32_t err_decode;
+  uint32_t err_lora_tx;
+  FaultType last_error;
 };
 
 struct SenderStatus {