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-admin-v2/node_modules/canvas/src/Util.h

@@ -0,0 +1,9 @@
+#pragma once
+
+#include <cctype>
+
+inline bool streq_casein(std::string& str1, std::string& str2) {
+  return str1.size() == str2.size() && std::equal(str1.begin(), str1.end(), str2.begin(), [](char& c1, char& c2) {
+    return c1 == c2 || std::toupper(c1) == std::toupper(c2);
+  });
+}