aqhome-nodes: send heartbeat message to interface every 2mins.

e02 now expects this message. If for at least 10mins no such msg is
received the USB interface is reset.

aqhome/msg/node/m_heartbeat.h

@@ -0,0 +1,28 @@
+/****************************************************************************
+ * This file is part of the project AqHome.
+ * AqHome (c) by 2026 Martin Preuss, all rights reserved.
+ *
+ * The license for this file can be found in the file COPYING which you
+ * should have received along with this file.
+ ****************************************************************************/
+
+#ifndef AQH_M_HEARTBEAT_H
+#define AQH_M_HEARTBEAT_H
+
+
+#include <aqhome/api.h>
+#include <aqhome/ipc2/message.h>
+
+#include <gwenhywfar/debug.h>
+
+
+AQHOME_API AQH_MESSAGE *AQH_HeartbeatMessage_new(uint8_t destAddr, uint8_t srcAddr, uint8_t code, uint32_t timestamp);
+AQHOME_API uint32_t AQH_HeartbeatMessage_GetTimestamp(const AQH_MESSAGE *msg);
+
+AQHOME_API void AQH_HeartbeatMessage_DumpToBuffer(const AQH_MESSAGE *msg, GWEN_BUFFER *dbuf, const char *sText);
+
+
+
+
+
+#endif