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/pages/AdminPromoGroups.tsx

@@ -4,6 +4,7 @@ import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
 import { useTranslation } from 'react-i18next';
 import { promocodesApi, PromoGroup } from '../api/promocodes';
 import { usePlatform } from '../platform/hooks/usePlatform';
+import { useFocusTrap } from '../hooks/useFocusTrap';
 
 // Icons
 const BackIcon = () => (
@@ -61,6 +62,9 @@ export default function AdminPromoGroups() {
   const { capabilities } = usePlatform();
 
   const [deleteConfirm, setDeleteConfirm] = useState<number | null>(null);
+  const deleteDialogRef = useFocusTrap<HTMLDivElement>(!!deleteConfirm, {
+    onEscape: () => setDeleteConfirm(null),
+  });
 
   // Query
   const { data: groupsData, isLoading } = useQuery({
@@ -216,8 +220,20 @@ export default function AdminPromoGroups() {
       {/* Delete Confirmation */}
       {deleteConfirm && (
         <div className="fixed inset-0 z-50 flex items-center justify-center p-4">
-          <div className="w-full max-w-sm rounded-xl bg-dark-800 p-6">
-            <h3 className="mb-2 text-lg font-semibold text-dark-100">
+          <div
+            className="absolute inset-0 bg-black/60"
+            onClick={() => setDeleteConfirm(null)}
+            aria-hidden="true"
+          />
+          <div
+            ref={deleteDialogRef}
+            role="dialog"
+            aria-modal="true"
+            aria-labelledby="promo-group-delete-title"
+            tabIndex={-1}
+            className="relative w-full max-w-sm rounded-xl bg-dark-800 p-6"
+          >
+            <h3 id="promo-group-delete-title" className="mb-2 text-lg font-semibold text-dark-100">
               {t('admin.promoGroups.confirm.title')}
             </h3>
             <p className="mb-6 text-dark-400">{t('admin.promoGroups.confirm.text')}</p>