The test_attachments_category_change_handling test was failing in CI with
HTTP 412 Precondition Failed errors. This is caused by the background vector
scanner (runs every 10 seconds) modifying notes between when the test fetches
the ETag and when it attempts to update the category.
Solution: Added retry logic (up to 3 attempts) that refetches the latest ETag
and retries the update operation when encountering 412 errors. This handles
the race condition gracefully while still catching genuine errors.
