fix: limited (traffic exhausted) subscription shows as expired

- Dashboard card: change date label from "Истекла" to "Активна до"
  for limited subscriptions (traffic exhausted but time remaining)
- Dashboard button: change text from "Трафик исчерпан" (dead-end) to
  "Докупить трафик" (actionable) for limited status
- Subscription page: CountdownTimer shows remaining time for limited
  subs instead of "Истекла" (was passing is_active=false)
- PurchaseCTAButton: don't treat limited as expired — limited subs
  still have time, should show extend CTA not "buy new subscription"

src/components/subscription/PurchaseCTAButton.tsx

@@ -15,7 +15,9 @@ export default function PurchaseCTAButton({
 }: PurchaseCTAButtonProps) {
   const { t } = useTranslation();
 
-  const isExpired = !subscription || (!subscription.is_active && !subscription.is_trial);
+  const isExpired =
+    !subscription ||
+    (!subscription.is_active && !subscription.is_trial && !subscription.is_limited);
   const isTrial = subscription?.is_trial;
   const isDaily = subscription?.is_daily;