Renames the product-catalogue pages (items + vendors, incl. their [id] detail
pages) out of /inventory into /catalogue. /inventory/cart is unchanged. All
internal links, redirects, revalidatePath calls, sidebar nav, and tests are
updated; next.config redirects keep old /inventory/{items,vendors}[/...] URLs
working (permanent) so existing bookmarks don't 404.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>