v1.0.5: Heltec V3 support, heap stability fix, TCP reconnection improvements

- Add Heltec WiFi LoRa 32 V3 board support (8MB flash, 8MB PSRAM)
  - New heltec_V3_boundary build environment in platformio.ini
  - Board auto-detection in flash.py (8MB=V3, 16MB=V4)
  - V3 board definition in Boards.h
- Fix heap exhaustion causing watchdog reboots every ~70 min
  - Lower boundary_mentioned_addresses cap from 512 to 200
  - Heap now stable at ~38KB free (was draining to 0)
- TCP reconnection improvements in TcpInterface.h
  - SO_LINGER(0) for clean socket teardown
  - 10-minute read timeout prevents zombie connections
  - Defensive client cleanup on accept
- Add heap telemetry instrumentation (HEAP-TEL) for monitoring
- Add level guards on TRACE/DEBUG macros in Log.h
- Update README for dual V3/V4 board support

RNode_Firmware.ino

@@ -635,7 +635,8 @@ void setup() {
       RNS::Transport::set_transmit_packet_callback(on_transmit_packet);
 
       Serial.write("Starting RNS...\r\n");
-      RNS::loglevel(RNS::LOG_TRACE);
+      RNS::loglevel(RNS::LOG_VERBOSE);
+      //RNS::loglevel(RNS::LOG_TRACE);
       //RNS::loglevel(RNS::LOG_MEM);
 
       HEAD("Registering LoRA Interface...", RNS::LOG_TRACE);
@@ -701,6 +702,9 @@ void setup() {
             0,
             "LocalTcpInterface"
         );
+        // rnsd can be quiet for long stretches — use 10 min timeout
+        // to prevent unnecessary reconnection cycles that leak lwIP memory
+        local_tcp_interface_ptr->setReadTimeout(600000);
         local_tcp_rns_interface = local_tcp_interface_ptr;
         local_tcp_rns_interface.mode(RNS::Type::Interface::MODE_ACCESS_POINT);
         RNS::Transport::register_interface(local_tcp_rns_interface);