Fix remaining localhost fallback in playground Request URL display

The previous fix only addressed line 251, but line 1074 still had a
hardcoded "localhost" fallback for the Request URL display section.
Now both occurrences use window.location.hostname as the fallback.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: surinderunitone

ui/src/app/playground/page.tsx

@@ -1071,7 +1071,7 @@ export default function PlaygroundPage() {
                     <span className="font-medium text-sm">Request URL</span>
                   </div>
                   <div className="font-mono text-sm break-all">
-                    {selectedRoute.protocol}://{selectedRoute.listener.hostname || "localhost"}:
+                    {selectedRoute.protocol}://{selectedRoute.listener.hostname || (typeof window !== "undefined" ? window.location.hostname : "localhost")}:
                     {selectedRoute.bindPort}
                     {request.path}
                   </div>