feat(ecommerce): badge antes/ahora en tarjetas de producto

Reutiliza Product.compareAtPrice (ya calculado en el provider de Medusa
via original_amount > calculated_amount) para mostrar precio tachado +
badge de descuento en la grilla/catalogo, no solo en la ficha de
producto. ADR 0005 seccion 3, patron Walmart -- cero cambio de modelo
de datos.

workloads/ecommerce/components/product/product-card.tsx

@@ -16,19 +16,29 @@ export function ProductCard({ product, priority = false }: { product: Product; p
   const wishlistHydrated = useWishlistStore((state) => state.hasHydrated);
   const toggleProduct = useWishlistStore((state) => state.toggleProduct);
   const isFavorite = wishlistHydrated && wishlistProducts.some((item) => item.id === product.id);
+  const discountPercent =
+    product.compareAtPrice && product.price
+      ? Math.round((1 - product.price / product.compareAtPrice) * 100)
+      : null;
 
   return (
     <article className="group flex h-full flex-col overflow-hidden rounded-3xl border border-slate-100 bg-white shadow-lg shadow-slate-900/5 transition duration-300 hover:-translate-y-1.5 hover:shadow-2xl hover:shadow-violet-500/10">
       <div className="relative aspect-square overflow-hidden bg-slate-50">
         <Link href={`/product/${product.slug}`} prefetch={false}><Image src={product.thumbnail} alt={product.name} fill priority={priority} sizes="(max-width: 640px) 82vw, (max-width: 1024px) 44vw, 280px" className="object-cover transition duration-500 group-hover:scale-[1.035]" /></Link>
-        <div className="absolute left-3 top-3 flex gap-2">{product.isNew && <Badge className="bg-fuchsia-500 text-white">Nuevo</Badge>}{product.featured && <Badge className="bg-yellow-300 text-slate-950"><Sparkles className="mr-1 size-3" />Top</Badge>}</div>
+        <div className="absolute left-3 top-3 flex gap-2">{discountPercent && discountPercent > 0 && <Badge className="bg-rose-600 text-white">-{discountPercent}%</Badge>}{product.isNew && <Badge className="bg-fuchsia-500 text-white">Nuevo</Badge>}{product.featured && <Badge className="bg-yellow-300 text-slate-950"><Sparkles className="mr-1 size-3" />Top</Badge>}</div>
         <button type="button" aria-label={isFavorite ? "Quitar de favoritos" : "Agregar a favoritos"} aria-pressed={isFavorite} className={`absolute right-3 top-3 rounded-full p-2.5 shadow-lg backdrop-blur transition ${isFavorite ? "bg-fuchsia-500 text-white" : "bg-white/95 text-slate-900 hover:text-fuchsia-500"}`} onClick={() => toggleProduct(product)}><Heart className={`size-4 ${isFavorite ? "fill-current" : ""}`} /></button>
       </div>
       <div className="flex flex-1 flex-col space-y-3 p-5">
         <div className="flex items-center justify-between gap-2 text-xs font-bold text-slate-500"><span>{product.category}</span><span className="rounded-full bg-cyan-50 px-2 py-1 text-cyan-700">{product.collection}</span></div>
         <Link href={`/product/${product.slug}`} prefetch={false}><h3 className="line-clamp-2 min-h-12 text-lg font-black leading-6 text-slate-950 group-hover:text-fuchsia-600">{product.name}</h3></Link>
         <p className="line-clamp-2 min-h-10 text-sm leading-5 text-slate-500">{product.shortDescription}</p>
-        <div className="mt-auto flex items-center justify-between gap-3 pt-1"><strong className="text-sm font-black">{formatMoney(product.price, product.currency)}</strong><Button variant="magenta" size="sm" onClick={() => addItem(product, product.variants[0]?.id)}><ShoppingBag className="size-4" />Agregar</Button></div>
+        <div className="mt-auto flex items-center justify-between gap-3 pt-1">
+          <div className="flex flex-col">
+            {product.compareAtPrice && <span className="text-xs font-bold text-slate-400 line-through">{formatMoney(product.compareAtPrice, product.currency)}</span>}
+            <strong className="text-sm font-black">{formatMoney(product.price, product.currency)}</strong>
+          </div>
+          <Button variant="magenta" size="sm" onClick={() => addItem(product, product.variants[0]?.id)}><ShoppingBag className="size-4" />Agregar</Button>
+        </div>
       </div>
     </article>
   );