feat: add contact fallback to opportunity cards

[antiisnotfound]

Implements Task 32 — opportunity cards now show the best available contact option (email → LinkedIn → name → org website → offer link).
Tested all 4 fallback paths manually.

[JossGeek]

Hi @antiisnotfound it looks like you omitted to support the "Contact" on Offer creation form:

you can add a specific contact section in the Offer form like this:

[antiisnotfound]

Thank you @JossGeek! I added the Contact Information section (Name, Phone, Email, LinkedIn) to the form like you suggested, but I kept it optional, since that's the whole point of the fallback logic. Take a look whenever you can.

[JossGeek]

great ! :)