The loading.tsx files for products/[id], sprint/[sprintId], and
sprint/[sprintId]/planning were 100% identical hand-rolled animate-pulse markup.
Extract the shape into components/loading/backlog-page-skeleton.tsx using the
shadcn <Skeleton> component, and re-export it from the three loading files.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
