turning into redoing all of the webrtc reading and publishing client side lol

webui/src/hooks/useServerUrl.js

@@ -0,0 +1,8 @@
+import { useCallback } from 'react';
+import { useSessionSelector } from '../context/SessionContext.jsx';
+
+export default function useServerUrl() {
+  const publicUrl = useSessionSelector((state) => state.session?.interInstances?.profile?.publicUrl);
+  // The UI may be served by Vite while session data comes from the actual server.
+  return useCallback((url) => new URL(url, publicUrl || window.location.origin).href, [publicUrl]);
+}