Decouple sender meter reads and harden meter RX robustness

src/meter_driver.cpp

@@ -4,7 +4,9 @@
 #include <stdlib.h>
 #include <string.h>
 
-static constexpr uint32_t METER_FRAME_TIMEOUT_MS = 1500;
+// LoRa TX/RX windows can block the main loop for several seconds at SF12.
+// Keep partial frame state long enough so valid telegrams are not dropped.
+static constexpr uint32_t METER_FRAME_TIMEOUT_MS = 20000;
 static constexpr size_t METER_FRAME_MAX = 512;
 
 enum class MeterRxState : uint8_t {
@@ -24,6 +26,10 @@ static uint32_t g_rx_timeout = 0;
 static uint32_t g_last_log_ms = 0;
 
 void meter_init() {
+#ifdef ARDUINO_ARCH_ESP32
+  // Buffer enough serial data to survive long LoRa blocking sections.
+  Serial2.setRxBufferSize(8192);
+#endif
   Serial2.begin(9600, SERIAL_7E1, PIN_METER_RX, -1);
 }