Add hover and focus state to neighborhood cards

On desktop, the neighborhood cards should have a hover effect to indicate that they're clickable. We could do something like `opacity: 0.8` to achieve that.

Secondly, the cards can already be tab-focussed but they don't get the blue outline. It'd be nice to have that as well.

Find the neighborhood card component and its styles, then start by locating how the cards are made keyboard-focusable. Add a visible desktop hover treatment and blue focus outline, and verify both mouse and keyboard states in the website.

Written by the indexing model from the issue text.