desk: fix full-width footer — scope .desk card rule to .row.desk
.desk { background/padding:50px/box-shadow } was the content-row 'card' styling
but the bare .desk selector also matched body.desk, padding the <body> 50px.
Since footer-home (#dw-footer, direct body child on classic pages) is width:100%,
it resolved to the padded body content width (1180px) instead of full width.
Scoped the rule to .row.desk so only the content row gets the card.
