Reissue Beta Invite

Replace an own active or expired invite with a fresh link (#1595).

For a recipient who lost the link: only the hash is stored, so the URL cannot be shown again. The old invite is revoked and a new one carrying the same label is minted in one transaction; the quota standing of an active invite is unchanged. Takes no body.

Args: invite_id: The invite to replace. request: FastAPI request (IP / User-Agent for the audit rows). user: Authenticated session user. db: Database session.

Returns: Exactly the create payload — the new invite and its plaintext URL, once.

Raises: NotFoundException: 404 — unknown id, or someone else's invite. BetaInviteAlreadyRedeemedError: 409 BETA-INVITE-002. BetaInviteAlreadyRevokedError: 409 BETA-INVITE-003 — also what the second request of a double-click gets; it mints nothing. BetaInviteQuotaExceededError: 409 BETA-INVITE-001 — an expired invite holds no slot, so reissuing one at the cap is refused (and the invite is left as it was).