fix(web): use http://api:3001 as default rewrite destination

next.config rewrites() runs at build time — API_INTERNAL_URL is not set
in CI, so the previous localhost:3001 fallback was baked into the bundle.
Default to http://api:3001 which is always correct in Docker network.

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

apps/web/next.config.ts

@@ -6,7 +6,7 @@ const withNextIntl = createNextIntlPlugin('./src/i18n/request.ts');
 const nextConfig: NextConfig = {
   output: 'standalone' as const,
   async rewrites() {
-    const apiUrl = process.env.API_INTERNAL_URL || 'http://localhost:3001';
+    const apiUrl = process.env.API_INTERNAL_URL || 'http://api:3001';
     return [
       {
         source: '/api-proxy/:path*',