feat: add environment variable support for admin user creation in backend

frontend/vue-app/src/components/shared/LoginButton.vue

@@ -147,8 +147,8 @@ const submit = async () => {
     if (!isPushOptedOut()) {
       subscribeToPushWithResult() // fire-and-forget — browser gesture is satisfied by the PIN button click
     }
-    close()
     const returnUrl = consumePendingReturnUrl()
+    close()
     router.push(returnUrl || '/parent')
   } catch (e) {
     error.value = 'Network error'