Resend an invitation email

Resends an invitation. Only works for pending invitations belonging to the user's company.

Two shapes, decided by the Cognito account status:

• FORCE_CHANGE_PASSWORD — an ordinary invitee who never signed in. Cognito re-sends the temporary password, as before.
• CONFIRMED — someone who already has a StandGest login (a self-signup account invited to join the company). admin_resend_invitation raises UnsupportedUserStateException for these, which used to make "Reenviar" a button that could never work; they get the branded tokenized link instead.

The expiry is pushed out too. Nothing in this codebase ever writes status='expired' — the row just sits 'pending' with a past expires_at — so re-sending a lapsed invitation used to hand out a working password and a token claim_invitation still refuses, with no way out of the loop.