Request a wallet ownership proof

Asks one of your existing end users to prove they control a self-hosted
(unhosted) EVM wallet. Supply the wallet address and the email of an end
user of yours; we email that user a secure hosted link where they sign a
one-time message with their wallet (EIP-191 personal_sign — no gas,
nothing broadcast on-chain). The signer is recovered and checked against the
address server-side; you observe the result via the returned status
(PENDING → VERIFIED). Returns 404 if the email is not a known end user of
your account. The hosted link is included in the response so you can share
it directly as well.