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/locales/ru.json

@@ -5405,7 +5405,9 @@
       "activateTelegram": "Активировать в Telegram",
       "activateWeb": "Активировать по почте",
       "emailLabel": "Ваш email",
-      "claimNow": "Получить подарок"
+      "claimNow": "Получить подарок",
+      "failedTitle": "Подарок недоступен",
+      "failedDesc": "Оплата подарка не прошла, поэтому активировать его нельзя."
     },
     "giftLink": {
       "shareText": "Дарю вам подписку! Активируйте здесь:",