Property creation via API returns 422 o:vocabulary missing

[tacman]

Summary\nCreating properties via the Omeka API fails with 422 "o:vocabulary must be set" even when a valid vocabulary exists and is referenced. Resource/item creation works.\n\n## Steps to Reproduce\n1. Ensure a custom vocabulary exists (e.g., prefix ).\n2. Call with payload like:\n\n3. API returns 422 with .\n\n## Observed Behavior\n- 422 response on \n- Error: must be set\n- Occurs with multiple payload variants (id, int, @id, full vocab object)\n\n## Expected Behavior\nProperty should be created when references a valid vocabulary.\n\n## Environment\n- Omeka S API\n- API key can create items/templates, but property creation fails\n- URL: https://kpa-omeka.survos.com