Always load user's theme from API if available, and update the localStorage cache. Previously in various situations the old cached value was being used instead, leading to inconsistent theming or wrong themeselector readout.

frontend/src/components/RestrictedAuth.vue

@@ -61,6 +61,7 @@ import { getSettings, uiBasePath } from '@/utils/settings'
 import { fetchJson, getUserFriendlyErrorMessage } from 'paskia'
 import RemoteAuthRequest from '@/components/RemoteAuthRequest.vue'
 import { focusDialogButton } from '@/utils/keynav'
+import { updateThemeFromSession } from '@/utils/theme'
 
 const props = defineProps({
   mode: {
@@ -147,6 +148,7 @@ async function fetchSettings() {
 async function validateSession() {
   try {
     session.value = await fetchJson('/auth/api/validate', { method: 'POST' })
+    updateThemeFromSession(session.value?.ctx)
     if (isAuthenticated.value && props.mode !== 'reauth') {
       currentView.value = 'forbidden'
       emit('forbidden', session.value)