Refactor LoRa protocol to batch+ack with ACK-based time bootstrap

include/lora_transport.h

@@ -6,11 +6,14 @@
 
 constexpr size_t LORA_MAX_PAYLOAD = 230;
 
+enum class LoraMsgKind : uint8_t {
+  BatchUp = 0,
+  AckDown = 1
+};
+
 struct LoraPacket {
-  uint8_t protocol_version;
-  DeviceRole role;
+  LoraMsgKind msg_kind;
   uint16_t device_id_short;
-  PayloadType payload_type;
   uint8_t payload[LORA_MAX_PAYLOAD];
   size_t payload_len;
   int16_t rssi_dbm;