fix: Format price display in ProductCard component

- Update the price formatting in ProductCard.vue to use `toLocaleString` to add thousand mark separators.

src/components/market/ProductCard.vue

@@ -127,7 +127,7 @@ const handleImageError = () => {
 
 const formatPrice = (price: number, currency: string) => {
   if (currency === 'sat') {
-    return `${price} sats`
+    return `${price.toLocaleString('en-US')} sats`
   }
   return new Intl.NumberFormat('en-US', {
     style: 'currency',