fix: Remove duplicate index number from card BACK label in CardList

src/components/flashcards/CardList.tsx

@@ -39,9 +39,6 @@ export function CardList({ cards }: CardListProps) {
             </div>
             <div>
               <div className="text-xs font-medium text-text-muted uppercase tracking-wider mb-2 flex items-center gap-2">
-                <span className="w-6 h-6 rounded-full bg-bg-surface-alt flex items-center justify-center text-text-secondary">
-                  {index + 1}
-                </span>
                 Back
               </div>
               <div className="markdown-content text-sm text-text-body bg-bg-base/50 p-4 rounded-xl border border-border-light/50">