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/apps/pos/src/app/(terminal)/page.tsx

@@ -1659,14 +1659,16 @@ export default function RegisterPage() {
           ))}
         </div>
         <div className="mt-3 grid grid-cols-2 gap-2">
-          <button
-            type="button"
-            onClick={() => void parkSale()}
-            disabled={processing || cart.length === 0}
-            className="min-h-16 rounded-xl bg-amber-500 text-lg font-bold text-white disabled:opacity-40"
-          >
-            {processing ? 'Guardando…' : 'Guardar pendiente'}
-          </button>
+          {!isSelfpayMode && (
+            <button
+              type="button"
+              onClick={() => void parkSale()}
+              disabled={processing || cart.length === 0}
+              className="min-h-16 rounded-xl bg-amber-500 text-lg font-bold text-white disabled:opacity-40"
+            >
+              {processing ? 'Guardando…' : 'Guardar pendiente'}
+            </button>
+          )}
           <button
             type="button"
             onClick={() => void confirmSale()}
@@ -1677,7 +1679,9 @@ export default function RegisterPage() {
               paidCents <= 0 ||
               paidCents > totals.total
             }
-            className="min-h-16 rounded-xl bg-[#1B4332] text-lg font-bold text-white disabled:opacity-40"
+            className={`min-h-16 rounded-xl bg-[#1B4332] text-lg font-bold text-white disabled:opacity-40 ${
+              isSelfpayMode ? 'col-span-2' : ''
+            }`}
           >
             {processing ? 'Confirmando…' : 'Cobrar e imprimir'}
           </button>
@@ -1688,7 +1692,7 @@ export default function RegisterPage() {
           disabled={processing || cart.length === 0}
           className="mt-2 w-full rounded-xl border border-gray-300 bg-white py-2 text-sm font-bold text-red-600 disabled:opacity-40"
         >
-          Vaciar caja
+          {isSelfpayMode ? '🧹 Limpiar Ticket' : 'Vaciar caja'}
         </button>
       </aside>