fix(storefront): polish cart

Fix real regression: the payment success checkmark and timeout clock
icons had been corrupted to literal '?' glyphs (confirmed via git
history — ✓ and ⏱ were replaced), so a customer who just paid saw a
confusing '?' instead of a success indicator. Restored both icons and
marked them aria-hidden since the adjacent heading already conveys
the status.

Add missing accessible names to icon-only buttons that had none:
quantity increase/decrease controls and the mobile delete button
(desktop remove button had a title attribute only, which is not
reliably announced by screen readers — added aria-label alongside it).
New cart.increaseQuantity/decreaseQuantity keys added across all
three locales.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/app/i18n/en.ts

@@ -105,6 +105,8 @@ export const en: Translations = {
     autoClose: 'Window will close automatically...',
     confirmClear: 'Are you sure you want to clear the cart?',
     removeItem: 'Remove item',
+    increaseQuantity: 'Increase quantity',
+    decreaseQuantity: 'Decrease quantity',
     paymentQrAlt: 'Payment QR code',
     acceptTerms: 'Please accept the offer terms, return policy, and warranty terms to proceed with the order.',
     copyError: 'Copy error:',