User feedback: pet profile pictures couldn't be enlarged. New
PetAvatarZoom client component wraps the profile avatar in a button —
clicking opens a lightbox Dialog showing the full photo, reusing
DialogContent's existing zoom-in-95 + fade entrance animation rather
than hand-rolling a new transition. A subtle hover scale + cursor-zoom-in
signals it's interactive. No-op when the pet has no avatar set (falls
back to initials, nothing to zoom into).