fix: rewrite /api/* to internal backend (localhost:3001), not public URL

The previous rewrite used NEXT_PUBLIC_API_URL (https://coop.hobokenchicken.com)
as the destination. This created a loop through Caddy: /api/* → Next.js →
rewrite to public URL → Caddy → Next.js → 502.

Now routes /api/* and /webhooks/* directly to the Express backend on
localhost:3001, bypassing Caddy entirely for API calls.

frontend/next.config.js

@@ -3,15 +3,14 @@ const nextConfig = {
   output: 'standalone',
   allowedDevOrigins: ['172.20.1.238'],
   async rewrites() {
-    const apiUrl = process.env.NEXT_PUBLIC_API_URL || 'http://localhost:3001';
     return [
       {
         source: '/api/:path*',
-        destination: `${apiUrl}/api/:path*`,
+        destination: 'http://localhost:3001/api/:path*',
       },
       {
         source: '/webhooks/:path*',
-        destination: `${apiUrl}/webhooks/:path*`,
+        destination: 'http://localhost:3001/webhooks/:path*',
       },
     ];
   },