fix(release): 0.2.8 harden admin proxy, cart stock caps, selfpay and refund timeline

- admin proxy: 25s timeout, body guards, structured failure logs
- cart: addItem enforces stock cap (409 INSUFFICIENT_STOCK), UI clamps qty
- tpv selfpay: hide sidebar/discounts/save-pending, rename button, receipt-settings 400 fix
- pos admin: quick products slot count aligned to 8
- returns: human-readable history message + metadata jsonb (migrations 064-065) + admin fallback formatter
- storefront: product card white background
- product page: remove duplicate stock label under add-to-cart button

project/frontend/src/app/products/[slug]/page.tsx

@@ -201,6 +201,7 @@ export default async function ProductPage({ params }: Props) {
               priceCents={grossCents}
               imageUrl={product.images?.[0]?.url}
               available={true}
+              availableQuantity={stock.availableQuantity}
               minPurchaseQty={product.minPurchaseQty ?? 1}
             />
           ) : (