Replace Telegram widget with bot login

lib/auth/telegram_session_stub.dart

@@ -1,3 +1,19 @@
 String telegramInitData() => '';
 
 String telegramLoginData() => '';
+
+String mapflowSessionToken() => '';
+
+String pendingTelegramLoginToken() => '';
+
+String telegramLoginTokenFromUrl() => '';
+
+void saveMapflowSessionToken(String token) {}
+
+void savePendingTelegramLoginToken(String token) {}
+
+void clearPendingTelegramLoginToken() {}
+
+void openExternalUrl(String url) {}
+
+void reloadApp() {}