feat: add multi-channel subscription blocking UI and admin management

- Channel subscription blocking screen with per-channel status display
- Safe URL handling with protocol validation (no open redirect)
- Race-condition-safe subscription check with useRef guard
- Admin channel management page with create, toggle, delete
- Error handlers on all admin mutations with haptic feedback
- Proper type guard for channel subscription error detection
- Accessibility: aria-labels on icon-only buttons
- Localization: en, ru, zh, fa translations

src/api/index.ts

@@ -12,6 +12,7 @@ export { infoApi } from './info';
 export { adminSettingsApi } from './adminSettings';
 export { adminApi, statsApi } from './admin';
 export { adminAppsApi } from './adminApps';
+export { adminChannelsApi } from './adminChannels';
 export { adminBroadcastsApi } from './adminBroadcasts';
 export { adminEmailTemplatesApi } from './adminEmailTemplates';
 export { adminPaymentMethodsApi } from './adminPaymentMethods';