chore(deps): upgrade to nextjs 16 (#2203)

* chore(deps): upgrade to nextjs 16

* upgraded fumadocs

* ensure vercel uses bun

* fix build

* fix bui;d

* remove redundant vercel.json

apps/docs/next.config.ts

@@ -16,10 +16,13 @@ const config = {
         destination: '/introduction',
         permanent: true,
       },
+    ]
+  },
+  async rewrites() {
+    return [
       {
-        source: '/docs/:path*.mdx',
+        source: '/:path*.mdx',
         destination: '/llms.mdx/:path*',
-        permanent: true,
       },
     ]
   },