feat: migrate Telegram Login Widget to v23 with admin-configurable settings

- Upgrade telegram-widget.js from v22 to v23 (TelegramLoginButton + ConnectedAccounts)
- TelegramLoginButton fetches widget config from API instead of hardcoded values
- Add TelegramWidgetConfig type and API method with fallback to env defaults
- Remove botUsername prop — now sourced from backend API
- Add useEffect cleanup to prevent orphaned iframes on unmount
- Add TELEGRAM_WIDGET category to admin interface settings menu
- Add i18n translations for widget settings (ru, en, zh, fa)

src/api/branding.ts

@@ -23,6 +23,14 @@ export interface EmailAuthEnabled {
   enabled: boolean;
 }
 
+export interface TelegramWidgetConfig {
+  bot_username: string;
+  size: 'large' | 'medium' | 'small';
+  radius: number;
+  userpic: boolean;
+  request_access: boolean;
+}
+
 export interface AnalyticsCounters {
   yandex_metrika_id: string;
   google_ads_id: string;
@@ -251,6 +259,24 @@ export const brandingApi = {
     }
   },
 
+  // Get Telegram widget config (public, no auth required)
+  getTelegramWidgetConfig: async (): Promise<TelegramWidgetConfig> => {
+    try {
+      const response = await apiClient.get<TelegramWidgetConfig>(
+        '/cabinet/branding/telegram-widget',
+      );
+      return response.data;
+    } catch {
+      return {
+        bot_username: import.meta.env.VITE_TELEGRAM_BOT_USERNAME || '',
+        size: 'large',
+        radius: 8,
+        userpic: true,
+        request_access: true,
+      };
+    }
+  },
+
   // Update analytics counters (admin only)
   updateAnalyticsCounters: async (data: Partial<AnalyticsCounters>): Promise<AnalyticsCounters> => {
     const response = await apiClient.patch<AnalyticsCounters>('/cabinet/branding/analytics', data);