feat: premenne {cena_s_kartou} a {zlava_s_kartou} v cenovkach (uloha 12)

- bezne produkty maju volitelne polia Cena s kartou / Zlava s kartou,
  vernostne produkty pouzivaju svoje existujuce hodnoty
- editor cenoviek: tlacidla na pridanie vrstiev a nahlad premennych
- jedinecne ID novych vrstiev (rychle pridanie viacerych vrstiev)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/app/page.tsx

@@ -835,6 +835,9 @@ export default function Home() {
         currentPriceMain={targetProduct?.priceMain || targetProduct?.cardPriceMain || '1'}
         currentPriceSub={targetProduct?.priceSub || targetProduct?.cardPriceSub || '99'}
         currentUnitPrice={targetProduct?.unitPrice || targetProduct?.cardUnitPrice || '1kg = 4,91 €'}
+        currentCardPriceMain={targetProduct?.cardPriceMain || undefined}
+        currentCardPriceSub={targetProduct?.cardPriceSub || undefined}
+        currentCardDiscount={targetProduct?.cardDiscount || undefined}
       />
 
       {/* Modál Moje newslettre (Ukladanie, duplikácia, vytváranie a prepínanie) */}