show NIP-05 address on profiles with npubs

[guaka]

e.g. [email protected]

Possibly with:

• hover to explain that this is not an email address
• suggestion to use https://www.0xchat.com/?
• if at all possible, a nostr messaging URL? (Reusing @ doesn't seem like the brightest idea at this point, but didn't dive into the rationale for this.)

Might as well fix #2693 while at it.