UI polish: consistent dropdowns and cleaner card hovers

Two visual fixes shipped across the whole platform today.

Dropdown menus (like the topic picker on the contact page) used to render as raw browser controls next to our styled text fields. Every dropdown now matches the text inputs -- same border, same focus ring, plus a proper chevron -- while keeping all the native keyboard and screen reader behavior.

And hovering over a card (a skill lab, a critique, a job listing) no longer underlines every line of text inside it at once, which was genuinely hard to read. Regular text links still underline on hover, exactly as before.