feat: replace text loading messages with PageSpinner component

Add a shared PageSpinner (spinning ring + optional label) and use it
in all pages that previously showed a plain text loading message:
home, stats, player, team, and tournament pages.

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

app/client.tsx

@@ -3,6 +3,7 @@ import { useQuery, gql } from '@/lib/graphql/hooks'
 import Link from 'next/link'
 import { TeamFlag } from '@/components/team-flag'
 import { LiveBadge } from '@/components/live-badge'
+import { PageSpinner } from '@/components/page-spinner'
 import { MatchCard } from '@/components/match-card'
 
 const HOME_QUERY = gql`
@@ -231,9 +232,7 @@ export function HomeClient() {
           </div>
         )}
 
-        {loading && !data && (
-          <div className="py-16 text-center text-green-muted text-sm">Loading live World Cup data…</div>
-        )}
+        {loading && !data && <PageSpinner />}
       </div>
     </div>
   )