Complete verification links and preserve verified login email (#60)

frontend/app/lib/routing/router.dart

@@ -135,7 +135,9 @@ GoRouter createAppRouter({bool Function()? authenticated}) {
       GoRoute(
         path: '/',
         name: AppRoutes.login,
-        builder: (context, state) => const AuthPage(),
+        builder: (context, state) => AuthPage(
+          email: state.extra is String ? state.extra as String : null,
+        ),
       ),
       GoRoute(
         path: '/verification-sent',