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/tournaments/[year]/page.tsx

@@ -72,6 +72,12 @@ export default function TournamentPage({ params }: { params: Promise<{ year: str
     if (el) el.scrollIntoView({ behavior: 'smooth', block: 'center' })
   }, [data])
 
+  useEffect(() => {
+    document.title = data?.tournament
+      ? `${year} World Cup · World Cup`
+      : `${year} · World Cup`
+  }, [data, year])
+
   const t = data?.tournament
   const standings: Standing[] = data?.groupStandings ?? []
   const byGroup = standings.reduce<Record<string, Standing[]>>((acc, s) => {