Addressable events (30818/30017) are author-signed, so "transferring" them
means re-signing each under the destination key + publishing, and optionally
publishing NIP-09 deletes for the originals. This script does that; it needs
TO_NSEC (destination) and, only for --delete-originals, FROM_NSEC. --dry-run
(default) needs no keys and just lists what would move.
