feat: add ButtonsTab for per-section button style customization

Visual editor in admin settings for configuring Telegram button colors
and custom emoji IDs per menu section. Includes API client, draft state
management, save/reset, and translations for ru/en/fa/zh locales.

src/components/admin/index.ts

@@ -6,6 +6,7 @@ export * from './SettingInput';
 export * from './SettingRow';
 export * from './AnalyticsTab';
 export * from './BrandingTab';
+export * from './ButtonsTab';
 export * from './ThemeTab';
 export * from './FavoritesTab';
 export * from './SettingsTab';