Tidied up the mentor contact card

A couple of small visual fixes to the card you see on every mentor profile when you're ready to reach out.

The "I know what I want to get out of this session" checkbox now uses the same styled checkbox every other form on the platform uses, instead of a plain, tiny browser default. We also added a clear "or" divider between the two ways to connect: booking directly online, or sending a structured mentorship request. That makes it obvious these are two separate paths, not one continuous flow.