fix: use config for turn

ui/src/app/api/config/turn/route.ts

@@ -0,0 +1,22 @@
+/*
+  Route to provide TURN server configuration at runtime.
+  This allows OSS users to configure TURN servers via docker-compose.yaml
+  environment variables, since NEXT_PUBLIC_* keys are injected at build time.
+*/
+import { NextResponse } from 'next/server';
+
+export async function GET() {
+  const host = process.env.TURN_HOST || '';
+  const username = process.env.TURN_USERNAME || '';
+  const password = process.env.TURN_PASSWORD || '';
+
+  // Only return enabled: true if all required fields are set
+  const enabled = !!(host && username && password);
+
+  return NextResponse.json({
+    enabled,
+    host,
+    username,
+    password,
+  });
+}