Set Host header for static app tunnel routing

src/server/tunnels.ts

@@ -180,6 +180,9 @@ function openTunnel(appName: string, port: number, subdomain?: string, isReconne
     onRequest(req) {
       const app = getApp(appName)
       if (app?.tunnelUrl) req.headers['x-app-url'] = app.tunnelUrl
+      // Static apps are served by the main server via subdomain routing,
+      // so set the Host header so extractSubdomain() can identify the app
+      if (app?.static) req.headers['host'] = `${appName}.localhost`
     },
 
     onOpen(assignedSubdomain) {