fix(gift): cabinet GiftResult shows claim link for directed gifts + review fixes

Pairs with the backend cabinet-unification. Directed cabinet gifts now stay
PAID/claimable, so the buyer's GiftResult must show the share link for them too.

- GiftResult.tsx: render the share state (and stop polling) for ANY claimable
  paid gift via is_claimable, not just is_code_only.
- api/gift.ts: GiftPurchaseStatus gains is_claimable.
- GiftClaim.tsx: explicit failed/expired state (was falling into the 'almost
  ready' spinner forever).
- PurchaseSuccess.tsx: a paid gift is always claimable — stop polling and show
  the share block on `paid && is_gift` (don't gate on is_claimable, which could
  strand the buyer on a spinner).
- i18n: landing.giftClaim.failedTitle/failedDesc in ru/en/zh/fa.

src/api/gift.ts

@@ -74,6 +74,7 @@ export interface GiftPurchaseStatus {
   status: GiftPurchaseStatusValue;
   is_gift: boolean;
   is_code_only: boolean;
+  is_claimable: boolean;
   purchase_token: string | null;
   recipient_contact_value: string | null;
   gift_message: string | null;