Removing the delete_content param means delete is always a soft delete, so
content created by one test now survives into the next. The suite had been
relying on hard-delete teardown for isolation, so shared fixed-content
fixtures started colliding: seeded_asset (b"A"*4096) and
make_asset_bytes (deterministic on name) produced the same hash every test,
so the second seed deduped to the surviving asset and returned 200 instead
of 201, cascading into ~14 failures/errors.
Salt both fixtures with a per-test uuid so each test creates fresh content
(created_new True, 201), while keeping content deterministic within a test
(same name/size -> same bytes) and preserving exact byte length so size-based
list/sort assertions are unaffected.