LivoxProto1: registerUdpHandler: enforce overwriting

Enforce handler overwriting in the devicesUnderConstruction
collection, for combos of cmd_set+cmd_id that pre-exist the
current invocation

commonLibs/livoxProto1/device.cpp

@@ -1896,12 +1896,25 @@ void Device::registerUdpCommandHandler(
 	 */
 	if (!deviceIP.empty())
 	{
-		// Add command-specific handler to the list for this device IP
+		auto& handlers = devicesUnderConstruction[deviceIP];
+		auto it = std::find_if(handlers.begin(), handlers.end(),
+			[cmd_set, cmd_id](const CommandHandler& existing) {
+				return existing.cmd_set == cmd_set && existing.cmd_id == cmd_id;
+			});
+
+		// Create the new command handler
 		CommandHandler cmdHandler;
 		cmdHandler.cmd_set = cmd_set;
 		cmdHandler.cmd_id = cmd_id;
 		cmdHandler.handler = std::move(handler);
-		devicesUnderConstruction[deviceIP].push_back(std::move(cmdHandler));
+
+		if (it != handlers.end()) {
+			// Replace existing handler
+			*it = std::move(cmdHandler);
+		} else {
+			// Add new handler
+			handlers.push_back(std::move(cmdHandler));
+		}
 	}
 }