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/AdminPolicies.tsx

@@ -5,6 +5,7 @@ import { useTranslation } from 'react-i18next';
 import { rbacApi, AccessPolicy, AdminRole } from '@/api/rbac';
 import { PermissionGate } from '@/components/auth/PermissionGate';
 import { usePlatform } from '@/platform/hooks/usePlatform';
+import { useFocusTrap } from '@/hooks/useFocusTrap';
 
 const BackIcon = () => (
   <svg
@@ -155,6 +156,9 @@ export default function AdminPolicies() {
   const { capabilities } = usePlatform();
 
   const [deleteConfirm, setDeleteConfirm] = useState<number | null>(null);
+  const deleteDialogRef = useFocusTrap<HTMLDivElement>(deleteConfirm !== null, {
+    onEscape: () => setDeleteConfirm(null),
+  });
   const [formError, setFormError] = useState<string | null>(null);
 
   // Queries
@@ -449,8 +453,15 @@ export default function AdminPolicies() {
             onClick={() => setDeleteConfirm(null)}
             aria-hidden="true"
           />
-          <div className="relative w-full max-w-sm rounded-xl border border-dark-700 bg-dark-800 p-6">
-            <h3 className="mb-2 text-lg font-semibold text-dark-100">
+          <div
+            ref={deleteDialogRef}
+            role="dialog"
+            aria-modal="true"
+            aria-labelledby="policy-delete-title"
+            tabIndex={-1}
+            className="relative w-full max-w-sm rounded-xl border border-dark-700 bg-dark-800 p-6"
+          >
+            <h3 id="policy-delete-title" className="mb-2 text-lg font-semibold text-dark-100">
               {t('admin.policies.confirm.title')}
             </h3>
             <p className="mb-6 text-dark-400">{t('admin.policies.confirm.text')}</p>