Adjust avatar border

[edwardshturman]

You gotta look closely but the cute yellow corners around avatars are actually not pixel perfect. Def more noticeable now after changing the avatars from AI pfps, where they had black backgrounds so u couldn't rly tell.

Idea from Ernesto: bake the border into the image (programmatically?)

Bonus idea from Ernesto: programmatic dithering/coloring of avatars to bring back the consistent look that the AI pfps had