Add RX reject reasons to telemetry and UI

BACKWARD-INCOMPATIBLE: MeterBatch schema bumped to v2 with err_rx_reject.
- Track and log RX reject reasons (CRC/protocol/role/payload/length/id/batch)
- Include rx_reject in sender telemetry JSON and receiver web UI
- Add lora_receive reject reason logging under SERIAL_DEBUG_MODE

src/data_model.cpp

@@ -8,3 +8,24 @@ void init_device_ids(uint16_t &short_id, char *device_id, size_t device_id_len)
   short_id = (static_cast<uint16_t>(mac[4]) << 8) | mac[5];
   snprintf(device_id, device_id_len, "dd3-%04X", short_id);
 }
+
+const char *rx_reject_reason_text(RxRejectReason reason) {
+  switch (reason) {
+    case RxRejectReason::CrcFail:
+      return "crc_fail";
+    case RxRejectReason::BadProtocol:
+      return "bad_protocol_version";
+    case RxRejectReason::WrongRole:
+      return "wrong_role";
+    case RxRejectReason::WrongPayloadType:
+      return "wrong_payload_type";
+    case RxRejectReason::LengthMismatch:
+      return "length_mismatch";
+    case RxRejectReason::DeviceIdMismatch:
+      return "device_id_mismatch";
+    case RxRejectReason::BatchIdMismatch:
+      return "batch_id_mismatch";
+    default:
+      return "none";
+  }
+}