feat(streaming): implement frame relay functionality for real-time video streaming and enhance client stream visibility

Backend/realtime/gateway.ts

@@ -26,6 +26,13 @@ const webrtcSignalSchema = z.object({
   data: z.record(z.string(), z.unknown()).nullable().optional(),
 });
 
+const streamFrameSchema = z.object({
+  toDeviceId: z.string().uuid(),
+  streamSessionId: z.string().uuid(),
+  frame: z.string().min(32),
+  capturedAt: z.string().optional(),
+});
+
 const roomForDevice = (deviceId: string): string => `device:${deviceId}`;
 
 let io: SocketIOServer | null = null;
@@ -233,6 +240,7 @@ export const setupRealtimeGateway = (server: HttpServer): SocketIOServer => {
   io.on('connection', async (socket) => {
     const auth = socket.data.deviceAuth as { userId: string; deviceId: string; role: 'camera' | 'client' };
     const deviceRoom = roomForDevice(auth.deviceId);
+    const verifiedRelayTargets = new Set<string>();
 
     socket.join(deviceRoom);
     await markDevicePresence(auth.deviceId, 'online');
@@ -321,6 +329,38 @@ export const setupRealtimeGateway = (server: HttpServer): SocketIOServer => {
       });
     });
 
+    socket.on('stream:frame', async (input) => {
+      const parsed = streamFrameSchema.safeParse(input);
+
+      if (!parsed.success) {
+        socket.emit('error:stream_frame', {
+          message: 'Invalid stream frame payload',
+          errors: parsed.error.flatten(),
+        });
+        return;
+      }
+
+      if (!verifiedRelayTargets.has(parsed.data.toDeviceId)) {
+        const targetDevice = await db.query.devices.findFirst({
+          where: and(eq(devices.id, parsed.data.toDeviceId), eq(devices.userId, auth.userId)),
+        });
+
+        if (!targetDevice) {
+          socket.emit('error:stream_frame', { message: 'Target device not found for this account' });
+          return;
+        }
+
+        verifiedRelayTargets.add(parsed.data.toDeviceId);
+      }
+
+      io?.to(roomForDevice(parsed.data.toDeviceId)).emit('stream:frame', {
+        fromDeviceId: auth.deviceId,
+        streamSessionId: parsed.data.streamSessionId,
+        frame: parsed.data.frame,
+        capturedAt: parsed.data.capturedAt ?? new Date().toISOString(),
+      });
+    });
+
     socket.on('disconnect', async () => {
       // Small delay allows fast reconnects to reuse presence without flapping.
       setTimeout(async () => {