CartItemView was registered on both /cart/items/ and
/cart/items/{item_uuid}/, so swagger listed POST/PATCH/DELETE on both
paths even though 3 of those 6 combinations raised a TypeError at
runtime (missing/unexpected item_uuid). Split into CartItemView (POST,
list path) and CartItemDetailView (PATCH/DELETE, detail path).
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>