v4.2.1 - Frontend polish & $REAL8 ticker

Changed

• $REAL8 ticker everywhere (product pages, cart, order details, payment instructions)
• Place Order button shows EUR + $REAL8 equivalent
• Cart total shows $REAL8 equivalent alongside fiat price
• Payment box full width on order-received page
• "REAL8 Total:" replaces old "Monto en Stellar:" label

Fixed

• QR code now renders (CDN URL was returning 404)
• Pay/Cancel buttons spaced apart with white text
• "Thank you" message hidden for pending REAL8 payments

Removed

• Redundant "Send Payment To:" heading on payment page