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/layout/AppShell/AppShell.tsx

@@ -18,6 +18,7 @@ import { cn } from '@/lib/utils';
 import WebSocketNotifications from '@/components/WebSocketNotifications';
 import CampaignBonusNotifier from '@/components/CampaignBonusNotifier';
 import SuccessNotificationModal from '@/components/SuccessNotificationModal';
+import { PromptDialogHost } from '@/components/PromptDialogHost';
 import LanguageSwitcher from '@/components/LanguageSwitcher';
 import TicketNotificationBell from '@/components/TicketNotificationBell';
 import { SubscriptionIcon, GiftIcon } from '@/components/icons';
@@ -278,7 +279,7 @@ export function AppShell({ children }: AppShellProps) {
   // headerHeight comes from useHeaderHeight() — accounts for TG safe area in fullscreen
 
   return (
-    <div className="min-h-screen">
+    <div className="min-h-viewport">
       {/* Animated background renders via portal on document.body at z-index: -1 */}
       <BackgroundRenderer />
 
@@ -286,6 +287,7 @@ export function AppShell({ children }: AppShellProps) {
       <WebSocketNotifications />
       <CampaignBonusNotifier />
       <SuccessNotificationModal />
+      <PromptDialogHost />
 
       {/* Desktop Header */}
       <header className="fixed left-0 right-0 top-0 z-50 hidden border-b border-dark-800/50 bg-dark-950/95 lg:block">
@@ -322,6 +324,7 @@ export function AppShell({ children }: AppShellProps) {
                 key={item.path}
                 to={item.path}
                 onClick={handleNavClick}
+                aria-label={item.label}
                 className={cn(
                   'group flex items-center rounded-xl px-2.5 py-2 transition-all duration-200',
                   isActive(item.path)
@@ -330,7 +333,7 @@ export function AppShell({ children }: AppShellProps) {
                 )}
               >
                 <item.icon className="h-[18px] w-[18px] shrink-0" />
-                <span className="max-w-0 overflow-hidden whitespace-nowrap text-xs font-medium opacity-0 transition-all duration-200 group-hover:ml-2 group-hover:max-w-40 group-hover:opacity-100">
+                <span className="max-w-0 overflow-hidden whitespace-nowrap text-xs font-medium opacity-0 transition-all duration-200 group-focus-within:ml-2 group-focus-within:max-w-40 group-focus-within:opacity-100 group-hover:ml-2 group-hover:max-w-40 group-hover:opacity-100">
                   {item.label}
                 </span>
               </Link>
@@ -339,6 +342,7 @@ export function AppShell({ children }: AppShellProps) {
               <Link
                 to="/referral"
                 onClick={handleNavClick}
+                aria-label={t('nav.referral')}
                 className={cn(
                   'group flex items-center rounded-xl px-2.5 py-2 transition-all duration-200',
                   isActive('/referral')
@@ -347,7 +351,7 @@ export function AppShell({ children }: AppShellProps) {
                 )}
               >
                 <UsersIcon className="h-[18px] w-[18px] shrink-0" />
-                <span className="max-w-0 overflow-hidden whitespace-nowrap text-xs font-medium opacity-0 transition-all duration-200 group-hover:ml-2 group-hover:max-w-40 group-hover:opacity-100">
+                <span className="max-w-0 overflow-hidden whitespace-nowrap text-xs font-medium opacity-0 transition-all duration-200 group-focus-within:ml-2 group-focus-within:max-w-40 group-focus-within:opacity-100 group-hover:ml-2 group-hover:max-w-40 group-hover:opacity-100">
                   {t('nav.referral')}
                 </span>
               </Link>
@@ -356,6 +360,7 @@ export function AppShell({ children }: AppShellProps) {
               <Link
                 to="/gift"
                 onClick={handleNavClick}
+                aria-label={t('nav.gift')}
                 className={cn(
                   'group flex items-center rounded-xl px-2.5 py-2 transition-all duration-200',
                   isActive('/gift')
@@ -364,7 +369,7 @@ export function AppShell({ children }: AppShellProps) {
                 )}
               >
                 <GiftIcon className="h-[18px] w-[18px] shrink-0" />
-                <span className="max-w-0 overflow-hidden whitespace-nowrap text-xs font-medium opacity-0 transition-all duration-200 group-hover:ml-2 group-hover:max-w-40 group-hover:opacity-100">
+                <span className="max-w-0 overflow-hidden whitespace-nowrap text-xs font-medium opacity-0 transition-all duration-200 group-focus-within:ml-2 group-focus-within:max-w-40 group-focus-within:opacity-100 group-hover:ml-2 group-hover:max-w-40 group-hover:opacity-100">
                   {t('nav.gift')}
                 </span>
               </Link>
@@ -375,6 +380,7 @@ export function AppShell({ children }: AppShellProps) {
                 <Link
                   to="/admin"
                   onClick={handleNavClick}
+                  aria-label={t('admin.nav.title')}
                   className={cn(
                     'group flex items-center rounded-xl px-2.5 py-2 transition-all duration-200',
                     location.pathname.startsWith('/admin')
@@ -383,7 +389,7 @@ export function AppShell({ children }: AppShellProps) {
                   )}
                 >
                   <ShieldIcon className="h-[18px] w-[18px] shrink-0" />
-                  <span className="max-w-0 overflow-hidden whitespace-nowrap text-xs font-medium opacity-0 transition-all duration-200 group-hover:ml-2 group-hover:max-w-40 group-hover:opacity-100">
+                  <span className="max-w-0 overflow-hidden whitespace-nowrap text-xs font-medium opacity-0 transition-all duration-200 group-focus-within:ml-2 group-focus-within:max-w-40 group-focus-within:opacity-100 group-hover:ml-2 group-hover:max-w-40 group-hover:opacity-100">
                     {t('admin.nav.title')}
                   </span>
                 </Link>
@@ -402,6 +408,9 @@ export function AppShell({ children }: AppShellProps) {
                 'rounded-xl border border-dark-700/50 bg-dark-800/50 p-2 text-dark-400 transition-colors duration-200 hover:bg-dark-700 hover:text-accent-400',
                 !canToggleTheme && 'pointer-events-none invisible',
               )}
+              aria-label={
+                isDark ? t('theme.light') || 'Light mode' : t('theme.dark') || 'Dark mode'
+              }
               title={isDark ? t('theme.light') || 'Light mode' : t('theme.dark') || 'Dark mode'}
             >
               {isDark ? <MoonIcon className="h-5 w-5" /> : <SunIcon className="h-5 w-5" />}