fix: use platformData.node/instance for correct guest grouping

The Dashboard grouping was broken because:
- node was set to r.parentId (full resource ID)
- instance was set to r.platformId

Fixed to read from platformData which contains the correct values:
- node = platformData.node (e.g., 'minipc')
- instance = platformData.instance (e.g., 'https://pve:8006')

This matches the legacy data format and fixes the grouped/list toggle.

frontend-modern/src/App.tsx

@@ -882,8 +882,8 @@ function App() {
             id: r.id,
             vmid: platformData?.vmid as number ?? 0,
             name: r.name,
-            node: r.parentId ?? '',
-            instance: r.platformId,
+            node: platformData?.node as string ?? '',
+            instance: platformData?.instance as string ?? r.platformId,
             status: r.status === 'running' ? 'running' : 'stopped',
             type: 'qemu',
             cpu: r.cpu?.current ?? 0,
@@ -926,8 +926,8 @@ function App() {
             id: r.id,
             vmid: platformData?.vmid as number ?? 0,
             name: r.name,
-            node: r.parentId ?? '',
-            instance: r.platformId,
+            node: platformData?.node as string ?? '',
+            instance: platformData?.instance as string ?? r.platformId,
             status: r.status === 'running' ? 'running' : 'stopped',
             type: 'lxc',
             cpu: r.cpu?.current ?? 0,