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/SuccessNotificationModal.tsx

@@ -10,6 +10,7 @@ import { useNavigate } from 'react-router';
 import { useSuccessNotification } from '../store/successNotification';
 import { useCurrency } from '../hooks/useCurrency';
 import { useTelegramSDK } from '../hooks/useTelegramSDK';
+import { useFocusTrap } from '../hooks/useFocusTrap';
 import { useHaptic } from '@/platform';
 
 // Icons
@@ -93,6 +94,9 @@ export default function SuccessNotificationModal() {
     hide();
   }, [hide]);
 
+  // Esc + scroll-lock are handled by the effects below; the trap only manages focus.
+  const modalRef = useFocusTrap<HTMLDivElement>(isOpen, { lockScroll: false });
+
   // Escape key to close
   useEffect(() => {
     if (!isOpen) return;
@@ -205,6 +209,11 @@ export default function SuccessNotificationModal() {
 
       {/* Modal */}
       <div
+        ref={modalRef}
+        role="dialog"
+        aria-modal="true"
+        aria-labelledby="success-modal-title"
+        tabIndex={-1}
         className="relative mx-4 w-full max-w-sm overflow-hidden rounded-3xl border border-dark-700/50 bg-dark-900 shadow-2xl"
         style={{
           marginBottom: safeBottom ? `${safeBottom}px` : undefined,
@@ -214,6 +223,7 @@ export default function SuccessNotificationModal() {
         {/* Close button */}
         <button
           onClick={handleClose}
+          aria-label={t('common.close')}
           className="absolute right-3 top-3 z-10 rounded-xl p-2 text-dark-400 transition-colors hover:bg-dark-800 hover:text-dark-200"
         >
           <CloseIcon />
@@ -224,7 +234,9 @@ export default function SuccessNotificationModal() {
           className={`flex flex-col items-center bg-gradient-to-br ${gradientClass} px-6 pb-8 pt-10`}
         >
           <div className="mb-4 animate-bounce text-white">{icon}</div>
-          <h2 className="text-center text-2xl font-bold text-white">{title}</h2>
+          <h2 id="success-modal-title" className="text-center text-2xl font-bold text-white">
+            {title}
+          </h2>
           {message && <p className="mt-2 text-center text-white/80">{message}</p>}
         </div>