refactor: adapt org-namespace lookup to principal name rename

Tracks the gpustack identity-consolidation effort: the unified
``principals`` table's URL-safe identifier column was renamed
``slug`` → ``name`` (with the legacy display ``name`` → ``display_name``).
The enterprise plugin's persisted org caches (``organizationList``,
``allOrganizations`` in localStorage) now write ``name`` instead of
``slug`` on each Organization row.

``getCurrentOrgNamespace`` reads those caches to compose the k8s
namespace (``gpustack-{name}``) for GPU-instance / storage CRDs.
Updated to read ``item.name`` so namespace resolution stays in sync
with what the enterprise plugin writes — otherwise every gpu-service
write would fall through to ``gpustack-default`` even when the user
has an Org context.

Stale ``slug`` references in surrounding comments also retitled to
``name`` to avoid divergence between code and prose. The namespace
format itself (``gpustack-{...}``) is unchanged — only the column it
sources is.

src/pages/gpu-service/instances/services/use-create-instance.ts

@@ -15,7 +15,7 @@ export default function useCreateInstance() {
   const currentCluster = useAtomValue(currentClusterAtom);
   const clusterID = currentCluster?.id;
   // Admin "All" view has no Org context — fall back to the
-  // selected cluster's owner Org slug for the K8s namespace.
+  // selected cluster's owner Org name for the K8s namespace.
   const namespace = getCurrentOrgNamespace(currentCluster?.owner_principal_id);
 
   const fetchDetail = useCallback(