fix: remove maximumDiskCacheSize unsupported by Next.js 16

The maximumDiskCacheSize option is not yet available in Next.js 16,
causing build failures. Revert this config change.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: Zheaoli

next.config.mjs

@@ -31,7 +31,6 @@ let nextConfig = {
         hostname: '**',
       },
     ],
-    maximumDiskCacheSize: 256 * 1024 * 1024,
   },
 }