Refactor Flutter app architecture

lib/shared/auth/telegram_session_stub.dart

@@ -0,0 +1,17 @@
+String telegramInitData() => '';
+
+String telegramLoginData() => '';
+
+String mapflowSessionToken() => '';
+
+String telegramLoginTokenFromUrl() => '';
+
+void saveMapflowSessionToken(String token) {}
+
+void clearMapflowSession() {}
+
+void configureTelegramWebApp() {}
+
+void openExternalUrl(String url) {}
+
+void reloadApp() {}