fix: dashboard offers card showing wrong counts

Queried status "converted"/"expired" but actual DB values are
"ordered"/"invalidated". Updated label "Prošlé" → "Zneplatněné".

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/admin/pages/Dashboard.tsx

@@ -493,7 +493,7 @@ export default function Dashboard() {
                     </span>
                   </div>
                   <div className="dash-stat-row">
-                    <span>Prošlé</span>
+                    <span>Zneplatněné</span>
                     <span className="admin-badge admin-badge-warning">
                       {dashData.offers.expired_count}
                     </span>