Replace standalone catalog editor with the unified Visual Catalog studio

Make /admin/catalog a full-screen catalog studio that replaces the old
listing plus separate [id]/builder-club detail pages:

- Embed CatalogManagerWorkspace on /admin/catalog with a Normal/Builder
  Club toggle, Catalog Sync status, packages (normal), Organize imports
  and a diagnostics link to /admin/studio/maintenance.
- Manage BC items directly in the studio Items tab (new BcItemsEditor,
  CRUD via existing bc actions; /api/admin/catalog/items now serves BC).
- Inline editor: add pageTextTeaser field for both catalogs and remove
  the legacy full-editor links.
- Remove the 'Open full editor' context action from the tree.
- Move catalog-items-table (dir + barrel) and catalog-translate-tab out
  of the app route into src/components/admin/catalog and update all
  importers.
- Keep /admin/catalog/[id], builder-club/[id] and /admin/catalog/maintenance
  as redirects into the new studio; consolidate maintenance panels into
  /admin/studio/maintenance and point the nav item there.
- Delete the old listing/table/tabs/forms and the standalone bc-manager.

src/lib/admin-nav.ts

@@ -452,11 +452,11 @@ export const ADMIN_NAV_GROUPS: AdminNavGroup[] = [
 				matchPrefixes: ["/admin/catalog"],
 			},
 			{
-				href: "/admin/catalog/maintenance",
+				href: "/admin/studio/maintenance",
 				labelKey: "catalogMaintenance",
 				icon: Wrench,
 				permission: PERMS.CATALOG_EDIT,
-				matchPrefixes: ["/admin/catalog/maintenance"],
+				matchPrefixes: ["/admin/studio/maintenance"],
 			},
 			{
 				href: "/admin/items",