fix(dashboard): suppress empty state flash while workloads are loading

The "No Proxmox VE nodes configured" message showed briefly on the
Workloads page because the empty-state guard didn't wait for the
workloads REST fetch to complete before deciding there were no guests.

frontend-modern/src/components/Dashboard/Dashboard.tsx

@@ -1202,6 +1202,7 @@ export function Dashboard(props: DashboardProps) {
         when={
           connected() &&
           initialDataReceived() &&
+          !workloads.loading() &&
           props.nodes.length === 0 &&
           allGuests().length === 0
         }