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/AdminNewsCreate.tsx

@@ -12,6 +12,7 @@ import UnderlineExtension from '@tiptap/extension-underline';
 import HighlightExtension from '@tiptap/extension-highlight';
 import { VideoExtension } from '../lib/tiptap-video';
 import { newsApi } from '../api/news';
+import { usePrompt } from '../store/promptDialog';
 import { AdminBackButton } from '../components/admin';
 import { ColoredItemCombobox } from '../components/admin/ColoredItemCombobox';
 import { Toggle } from '../components/admin/Toggle';
@@ -601,17 +602,21 @@ export default function AdminNewsCreate() {
   };
 
   // Toolbar actions
-  const addLink = () => {
-    const url = window.prompt(t('news.admin.toolbar.linkUrlPrompt'));
-    if (url && editor) {
-      try {
-        const parsed = new URL(url);
-        if (parsed.protocol !== 'https:' && parsed.protocol !== 'http:') return;
-      } catch {
-        return;
-      }
-      editor.chain().focus().setLink({ href: url }).run();
+  const promptDialog = usePrompt();
+  const addLink = async () => {
+    if (!editor) return;
+    const url = await promptDialog({
+      label: t('news.admin.toolbar.linkUrlPrompt'),
+      inputType: 'url',
+    });
+    if (!url) return;
+    try {
+      const parsed = new URL(url);
+      if (parsed.protocol !== 'https:' && parsed.protocol !== 'http:') return;
+    } catch {
+      return;
     }
+    editor.chain().focus().setLink({ href: url }).run();
   };
 
   if (isEdit && isLoadingArticle) {