EEF-CVE-2026-82738

Ash.Type.UUIDv7 accepts non-v7 UUIDs that then fail to load, causing persistent denial of service

## Summary Improper Input Validation vulnerability in ash-project ash allows an attacker to persistently deny reads of a record by storing a non-version-7 UUID in an `Ash.Type.UUIDv7` attribute. `Ash.Type.UUIDv7.cast_input/2` accepts any well-formed UUID string, including non-version-7 UUIDs, and stores it as a 16-byte binary. On read, `cast_stored/2` (`lib/ash/type/uuid_v7.ex`) routes the stored binary back through `cast_input/2`, which since an input-validation tightening in v3.6.3 matches only version-7 (and optionally version-4) 16-byte binaries and otherwise expects a 36-character string. A stored non-v7 16-byte binary matches neither clause and returns `:error`, so every later read of that record fails. An attacker able to set such an attribute poisons the row permanently. The fix decodes any 16-byte stored binary directly in `cast_stored/2`. This issue affects ash: from 3.6.3 before 3.32.2.