feat(a11y): cross-platform hardening + modal focus-trap from impeccable audit

Responsive / viewport:
- add .min-h-viewport / .h-viewport utilities (100dvh + Telegram --tg-viewport-stable-height)
- migrate min-h-screen / h-screen / 100vh across 18 files
- reveal hover-only controls on focus-within + touch (desktop nav, admin settings)
- grid breakpoints (TopUpAmount, Contests), larger touch targets, nav aria-labels

Platform routing (Telegram WebView correctness):
- clipboard -> copyToClipboard util with execCommand fallback (10 files)
- window.open -> openTelegramLink / openLink (Profile, Referral, ChannelSubscriptionScreen)
- window.confirm -> useNativeDialog (admin pages); PromoOffersSection -> useDestructiveConfirm
- window.prompt -> usePrompt / PromptDialogHost (TipTap link editors)
- ESLint no-restricted-properties guard against regressions (adapters/clipboard util exempt)

Modal accessibility:
- new useFocusTrap hook (focus trap, Esc, scroll lock, focus restore)
- role=dialog / aria-modal / focus-trap: Polls, SuccessNotificationModal, AdminPolicies,
  AdminPromoGroups, AdminCampaigns, BroadcastPreview (Telegram + Email)
- new global usePrompt store + PromptDialogHost

src/components/PromoOffersSection.tsx

@@ -4,7 +4,7 @@ import { useTranslation } from 'react-i18next';
 import { useNavigate } from 'react-router';
 import { promoApi, PromoOffer } from '../api/promo';
 import { ClockIcon, CheckIcon } from './icons';
-import { usePlatform } from '@/platform/hooks/usePlatform';
+import { useDestructiveConfirm } from '@/platform/hooks/useNativeDialog';
 
 // Helper functions
 const formatTimeLeft = (
@@ -88,7 +88,7 @@ export default function PromoOffersSection({ className = '' }: PromoOffersSectio
   const { t } = useTranslation();
   const navigate = useNavigate();
   const queryClient = useQueryClient();
-  const { dialog, capabilities } = usePlatform();
+  const confirmDeactivate = useDestructiveConfirm();
   const [claimingId, setClaimingId] = useState<number | null>(null);
   const [successMessage, setSuccessMessage] = useState<string | null>(null);
   const [errorMessage, setErrorMessage] = useState<string | null>(null);
@@ -160,36 +160,19 @@ export default function PromoOffersSection({ className = '' }: PromoOffersSectio
     navigate('/subscription/purchase');
   };
 
-  const handleDeactivateClick = () => {
+  const handleDeactivateClick = async () => {
     setErrorMessage(null);
     setSuccessMessage(null);
 
-    if (capabilities.hasNativeDialogs) {
-      dialog
-        .popup({
-          title: t('promo.deactivate.confirmTitle'),
-          message: t('promo.deactivate.confirmDescription', {
-            percent: activeDiscount?.discount_percent || 0,
-          }),
-          buttons: [
-            { id: 'cancel', type: 'cancel', text: '' },
-            { id: 'confirm', type: 'destructive', text: t('promo.deactivate.confirm') },
-          ],
-        })
-        .then((buttonId) => {
-          if (buttonId === 'confirm') {
-            deactivateMutation.mutate();
-          }
-        });
-    } else {
-      const confirmed = window.confirm(
-        t('promo.deactivate.confirmDescription', {
-          percent: activeDiscount?.discount_percent || 0,
-        }),
-      );
-      if (confirmed) {
-        deactivateMutation.mutate();
-      }
+    const confirmed = await confirmDeactivate(
+      t('promo.deactivate.confirmDescription', {
+        percent: activeDiscount?.discount_percent || 0,
+      }),
+      t('promo.deactivate.confirm'),
+      t('promo.deactivate.confirmTitle'),
+    );
+    if (confirmed) {
+      deactivateMutation.mutate();
     }
   };