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

node_modules/math-intrinsics/mod.js

@@ -0,0 +1,9 @@
+'use strict';
+
+var $floor = require('./floor');
+
+/** @type {import('./mod')} */
+module.exports = function mod(number, modulo) {
+	var remain = number % modulo;
+	return $floor(remain >= 0 ? remain : remain + modulo);
+};