CVE-2026-35172: Distribution: stale blob access resurrection via repo-scoped redis descriptor cache invalidation

distribution can restore read access in repo a after an explicit delete when storage.cache.blobdescriptor: redis and storage.delete.enabled: true are both enabled. the delete path clears the shared digest descriptor but leaves stale repo-scoped membership behind, so a later Stat or Get from repo b repopulates the shared descriptor and makes the deleted blob readable from repo a again.