The owner sees every new account, is notified, and can suspend or remove one; signups are audited #660

There is no way to see new accounts, no notification when one appears, and no way to suspend or delete an account — not even for the owner. Open signup needs all three.

Acceptance criteria

• [ ] A signup writes an audit record (who, when, from where) and notifies the owner.
• [ ] The owner has a page listing accounts with their created date, verified state, and what they own and have spent.
• [ ] The owner can suspend an account (its sessions and tokens stop working, it can start nothing) and can remove one (its content handled safely), through the product, with the action audited.
• [ ] Test: the owner suspends a fresh account and its token and session stop working at once; the owner removes it and it is gone.