- Drop unused 'result' assignment in clear_asset_preview_route (DELETE
returns 204, the result isn't needed).
- Remove unused 'pytest' import from test_preview.py.
- PUT /api/assets/{id}/preview: sets the preview asset for an existing asset,
returns the full updated Asset object. Returns 404 if asset ID doesn't exist.
- DELETE /api/assets/{id}/preview: clears the preview asset link, returns 204.
Returns 404 if asset ID doesn't exist.
Added OpenAPI spec entries under the assets tag with no x-runtime restriction.
Implemented handlers using the existing set_asset_preview service function.
Added integration tests covering happy paths and 404 cases.
Co-authored-by: Matt Miller <MillerMedia@users.noreply.github.com>
