fix(webapp): keep device presence alive via heartbeats

WebApp/src/lib/app/controller.js

@@ -72,6 +72,7 @@ const DEFAULT_CAMERA_CONSTRAINTS = {
 	height: { ideal: 360, max: 540 },
 	frameRate: { ideal: 15, max: 24 }
 };
+const SOCKET_HEARTBEAT_INTERVAL_MS = 10_000;
 
 const rtcConfig = {
 	iceServers: [{ urls: 'stun:stun.l.google.com:19302' }]
@@ -81,6 +82,7 @@ let initialized = false;
 let initPromise = null;
 let socket = null;
 let pollInterval = null;
+let socketHeartbeatInterval = null;
 let localCameraStream = null;
 let activeMediaRecorder = null;
 let activeRecordingChunks = [];
@@ -1414,10 +1416,34 @@ const handleCameraStreamRequest = async ({ streamId, requesterDeviceId }) => {
 	addActivity('Stream', 'Accepted stream request and started WebRTC offer');
 };
 
+const stopSocketHeartbeat = () => {
+	if (socketHeartbeatInterval) {
+		clearInterval(socketHeartbeatInterval);
+		socketHeartbeatInterval = null;
+	}
+};
+
+const emitSocketHeartbeat = () => {
+	if (!socket?.connected) {
+		return;
+	}
+
+	socket.emit('heartbeat');
+};
+
+const startSocketHeartbeat = () => {
+	stopSocketHeartbeat();
+	emitSocketHeartbeat();
+	socketHeartbeatInterval = setInterval(() => {
+		emitSocketHeartbeat();
+	}, SOCKET_HEARTBEAT_INTERVAL_MS);
+};
+
 const connectSocket = () => {
 	const { deviceToken } = getAppState();
 	if (!deviceToken) return;
 
+	stopSocketHeartbeat();
 	if (socket) socket.disconnect();
 	socket = io(getBackendUrl(), {
 		auth: { token: deviceToken },
@@ -1425,6 +1451,7 @@ const connectSocket = () => {
 	});
 
 	socket.on('connect', () => {
+		startSocketHeartbeat();
 		setAppState({ socketConnected: true });
 		addActivity('System', 'Connected to realtime server');
 		if (getAppState().device?.role === 'camera') {
@@ -1434,6 +1461,7 @@ const connectSocket = () => {
 	});
 
 	socket.on('disconnect', () => {
+		stopSocketHeartbeat();
 		setAppState({ socketConnected: false });
 		void stopLocalRecording();
 		teardownPeerConnection();
@@ -1443,6 +1471,7 @@ const connectSocket = () => {
 
 	socket.on('connect_error', (error) => {
 		const message = error?.message || 'Realtime connection failed';
+		stopSocketHeartbeat();
 		setAppState({ socketConnected: false });
 		addActivity('System', `Realtime connection failed: ${message}`);
 
@@ -1675,6 +1704,7 @@ const startPolling = () => {
 
 const cleanupConnectionState = async () => {
 	stopPolling();
+	stopSocketHeartbeat();
 	await stopLocalRecording();
 	teardownPeerConnection();
 	stopCameraPreview();