fix: guard against undefined route.name in auth layout check

route.name can be undefined during initial route resolution or for
unnamed routes. Without this guard, AUTH_ROUTE_NAMES.has() would
return false and the authenticated layout could flash briefly.

frontend/src/App.vue

@@ -58,7 +58,7 @@ const baseStore = useBaseStore()
 
 const route = useRoute()
 
-const showAuthLayout = computed(() => authStore.authUser && !AUTH_ROUTE_NAMES.has(route.name as string))
+const showAuthLayout = computed(() => authStore.authUser && typeof route.name === 'string' && !AUTH_ROUTE_NAMES.has(route.name))
 
 useBodyClass('is-touch', isTouchDevice())
 const keyboardShortcutsActive = computed(() => baseStore.keyboardShortcutsActive)