fix: update document.title on every page via useEffect

All pages are 'use client' so metadata exports don't work. Each page now
sets document.title via useEffect — static pages with a fixed string,
dynamic pages keyed on data so the title reflects the loaded content.

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

app/search/page.tsx

@@ -41,6 +41,10 @@ function SearchContent() {
     return () => clearTimeout(t)
   }, [q, router])
 
+  useEffect(() => {
+    document.title = q.trim() ? `"${q.trim()}" · World Cup` : 'Search · World Cup'
+  }, [q])
+
   const skip = debouncedQ.trim().length < 2
   const { data, loading } = useQuery(SEARCH_QUERY, {
     variables: { q: debouncedQ },