fix: review findings from full-diff audit (7 fixed)

- popularSearches sent translated display text as the actual search
  query instead of the canonical term - useSuggestion() now prefers
  target.query.q when present.
- CartService.addItem() dedup guard resolved immediately instead of
  awaiting the real in-flight add; now tracks the pending Promise per
  itemID so concurrent callers await the actual result.
- addItem()'s Promise never rejected on failure (resolve() in both
  next/error branches) - now rejects on error; buyNow() catches and
  shows an error toast instead of navigating on a failed add.
- Quick View had no stale-response guard - a slower earlier request
  could overwrite a faster later one. Added a request-generation
  counter.
- cart autoSubmitPurchase() set paymentStatus to null synchronously
  right after firing the async submit call, blanking the success
  screen while the request was still in flight. Removed the
  redundant/harmful line.
- Order terminal-status guard (cancelled/refunded can't be reopened)
  lived only in the page component. Moved enforcement into the
  gateway (single write path) via a shared TERMINAL_ORDER_STATUSES
  const, so no future caller can bypass it.
- TranslatePipe's per-instance memoization cache had no eviction,
  so bindings with volatile params (pagination counts) grew it
  unbounded for the component's lifetime. Capped at 50 entries.

Not changed: the dark-mode color override was flagged as clobbering
admin branding, but it's the exact palette explicitly requested this
session for the global dark default - not a bug.

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

src/app/pages/cart/cart.component.ts

@@ -499,7 +499,6 @@ export class CartComponent implements OnDestroy {
         this.router.navigate([`/${lang}`]);
       }
     });
-    this.paymentStatus.set(null);
   }
 
   copyPaymentLink(): void {