Major changes:
- Redesign cabinet with Linear-style components and top navigation
- Replace detail modals with dedicated pages (users, broadcasts, email templates)
- Add email channel support for broadcasts
- Remove pull-to-refresh, improve drag-and-drop on touch devices
- Fix Telegram Mini App: fullscreen, back button, scroll restoration
- Unify admin pages color scheme to design system
- Mobile-first improvements: horizontal tabs for settings, better touch targets
- Add zustand store for global success notifications
- Create SuccessNotificationModal component with prominent UI
- Update WebSocketNotifications to show modal for important events:
- balance.topup shows balance topped up modal
- subscription.activated shows activation modal
- subscription.renewed shows renewal modal
- Add translations for all locales (ru, en, zh, fa)
