fix(pwa): add turbopack config to silence next-pwa webpack warning

next-pwa registers a webpack config; Next.js 16 requires turbopack: {}
when a webpack config exists and no turbopack config is set.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

next.config.ts

@@ -25,6 +25,7 @@ const withPWA = withPWAInit({
 
 const nextConfig: NextConfig = {
   output: "standalone",
+  turbopack: {},
 };
 
 export default withPWA(nextConfig);