Declining a mentor request now comes with real options

A couple of follow-ups to the mentor requests inbox we shipped earlier today.

When a mentor declines a request, they can now choose from a few starter messages — not the right area of expertise, at capacity right now, or a suggestion to try async feedback through Critique instead — and edit any of them before sending, or write their own from scratch. It's optional; declining without a message still works exactly as before.

On the other side, a member's own request history now actually shows whether a mentor has responded. Previously there was no way to tell if a request had been seen at all. If it was declined, the member sees the mentor's message (if one was left) along with a link to get async feedback through Critique in the meantime.