feat: distinguish same-name GPU service resources across users

Resource names are unique per owning principal, so different users
can legally create same-name GPU instances, templates, SSH public
keys, storage volumes and storage types — but the admin's
cross-tenant lists and the instance-create template picker rendered
them indistinguishably.

- Group the template picker by owning scope: Your Templates, Global
  Templates, then — admin cross-tenant view only — one group per
  owner. A single group renders flat without headers. A plugin can
  take over grouping via hooks.useTemplateOwnerGroups when its
  principal model scopes templates beyond USER owners; a plugin
  without the hook keeps the flat list.
- Add an admin-only Creator column to the Instances, SSH Public
  Keys, Storage and Storage Types tables, sitting right before
  Created (mirroring the API Keys page convention). Resolves
  creator_id to a username via the user directory, falling back to
  owner_principal_id for legacy rows — a personal-scope row's
  creator IS its owner.
- Tag template cards with their owner scope (Global / username) for
  admins.

The Creator column and the card tag defer to a plugin that registers
the page's list columns / the OwnerScopeTag slot. Requires the
gpustack server change that records creator_id on templates, SSH
public keys and storage types.

src/pages/gpu-service/instances/config/types.ts

@@ -110,6 +110,7 @@ export interface ListItem extends FormData {
   created_at: string;
   updated_at: string;
   deleted_at?: string | null;
+  creator_id?: number | null;
   status?: InstanceStatus | null;
 }