feat: Passwordless cross-device authentication

- Arkitektur: docs/auth/passwordless-architecture.md
- Backend: iom/quixzoom-auth-service/ (FastAPI + Redis)
- Webb: quixzoom-market-pages/se/login/ (QR-kod + polling)
- App: iom/quixzoom-app/src/features/auth/ (push + deep links)

Flöde: QR-kod → app-godkännande → webb-inloggad

landvex/node_modules/readable-stream/experimentalWarning.js

@@ -0,0 +1,17 @@
+'use strict'
+
+var experimentalWarnings = new Set();
+
+function emitExperimentalWarning(feature) {
+  if (experimentalWarnings.has(feature)) return;
+  var msg = feature + ' is an experimental feature. This feature could ' +
+       'change at any time';
+  experimentalWarnings.add(feature);
+  process.emitWarning(msg, 'ExperimentalWarning');
+}
+
+function noop() {}
+
+module.exports.emitExperimentalWarning = process.emitWarning
+  ? emitExperimentalWarning
+  : noop;