fix: Card pictures position and border-radius

[Simandre]

Fixes:

Pictures in cards have border-radius set at the bottom instead of top (changed the respective bootstrap class):

Pictures now stick to the bottom of the card instead of its previous sibling, moving whitespace at the bottom of smaller cards of a row, to the space between the picture and the text:

On fold-like sizes, cards are centered like other biggers sizes (was left aligned):

[binokochumolvarghese]

Thank ou @EttSimon for the contribution.