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/validator/es/lib/isMagnetURI.js

@@ -0,0 +1,9 @@
+import assertString from './util/assertString';
+var magnetURIComponent = /(?:^magnet:\?|[^?&]&)xt(?:\.1)?=urn:(?:(?:aich|bitprint|btih|ed2k|ed2khash|kzhash|md5|sha1|tree:tiger):[a-z0-9]{32}(?:[a-z0-9]{8})?|btmh:1220[a-z0-9]{64})(?:$|&)/i;
+export default function isMagnetURI(url) {
+  assertString(url);
+  if (url.indexOf('magnet:?') !== 0) {
+    return false;
+  }
+  return magnetURIComponent.test(url);
+}