`.avatar-grid`s have layout shift as images load

[charmander]

.avatar-grids are the lists of users present in:

• the staff list
• user search results
• following, pending friends, and accepted friends settings pages (these ones include buttons)
• user profile following and follower pages

In CSS, we should reserve the normal (maximum) avatar space for all cells. Make sure:

• avatars smaller than the maximum size are centered
• avatars scale properly in narrower containers (no overflow, remain square; ideally, smaller avatars only start to scale when they need to, but if they scale in proportion that’s fine too)