RotateDepositAddress

Admin (DepositAddressRotate): supersede a user's PROVABLY DEAD deposit address (the signer can no longer unseal its key — the KEK-epoch casualty class) with a freshly minted keypair, and refresh the hub's address cache. The signer refuses to rotate a key that still unseals. Funds already on the old address remain unrecoverable; this restores the user's ability to receive FUTURE deposits.