fix(feed): video covers fill the square thumbnail (object-fit:cover), centered — incl. desktop
The desktop list-cover rule was .post-list-cover img (img only), so a federated <video> cover was
unstyled = rendered at its intrinsic size (e.g. 640x360), overflowing the square slot from the
top-left. Add video to that rule so it gets width/height:100% + object-fit:cover + center (fill the
square, keep aspect, crop the overflow). Reverted the earlier object-fit:contain — the ask is cover,
not letterbox. style.css buster 65 -> 66.
Co-Authored-By: Claude <noreply@…>