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/lib/emailRenderer.ts

@@ -830,7 +830,10 @@ function renderExactLoyaltyCard(p: any, validity: string): string {
                     priceMain: p.cardPriceMain || p.priceMain || '0',
                     priceSub: p.cardPriceSub || p.priceSub || '00',
                     discountText: p.cardDiscount || p.discountText || '',
-                    unitPrice: p.cardUnitPrice || p.unitPrice || ''
+                    unitPrice: p.cardUnitPrice || p.unitPrice || '',
+                    cardPriceMain: p.cardPriceMain,
+                    cardPriceSub: p.cardPriceSub,
+                    cardDiscount: p.cardDiscount
                   };
 
                   return `