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/zh.json

@@ -4509,7 +4509,9 @@
       "activateTelegram": "在 Telegram 中激活",
       "activateWeb": "通过邮箱激活",
       "emailLabel": "您的邮箱",
-      "claimNow": "领取礼物"
+      "claimNow": "领取礼物",
+      "failedTitle": "礼物不可用",
+      "failedDesc": "此礼物的付款未成功，无法激活。"
     },
     "giftLink": {
       "shareText": "我送您一份订阅！在此激活：",