fix(web): fix doubled section prefix in doc links (404 on click)

Home page, search results, and doc page Related links all
generated hrefs as /${section}/${slug} but slug already
includes the section prefix (e.g. 'docs/websocket/contract'),
producing doubled URLs like /docs/docs/websocket/contract → 404.
Fix: href={`/${d.slug}`} everywhere.

apps/web/app/page.tsx

@@ -35,7 +35,7 @@ export default async function Home() {
               {docs.map((d: DocumentMeta) => (
                 <li key={d.slug} className="py-2">
                   <Link
-                    href={`/${d.section}/${d.slug}`}
+                    href={`/${d.slug}`}
                     className="hover:underline font-medium"
                   >
                     {d.title}