fix: support 100% discount display + fix Telegram link widget race condition

- formatPrice shows "Бесплатно/Free" when price is 0 (SubscriptionPurchase, Subscription, RenewSubscription)
- Add subscription.free locale key (ru/en/zh/fa)
- Fix TelegramLinkWidget NS_BINDING_ABORTED: move legacy widget callback to ref pattern, remove unstable deps (showToast, t, navigate) from useEffect — prevents iframe destruction on re-render
- Clean up OIDC effect deps

src/locales/en.json

@@ -324,6 +324,7 @@
     "used": "Used",
     "of": "of",
     "renew": "Renew",
+    "free": "Free",
     "extend": "Extend Subscription",
     "buyTraffic": "Buy Traffic",
     "buyDevices": "Buy Devices",