Seeker Genesis Token verification

The Seeker Genesis Token (SGT) is a Token-2022 NFT minted once per Seeker device. Holding one is evidence of owning a Seeker, which makes it useful for gating rewards and for one-claim-per-device logic.

Verification has two halves, and both are required:

1. Prove the user controls the wallet — Sign-in-with-Solana (SIWS)
2. Prove that wallet holds an SGT — inspect the wallet's Token-2022 mints

Doing only the second means anyone can submit a real Seeker owner's public address and pass. Doing only the first proves wallet control but says nothing about a device.

This must run on a server

Never decide entitlement client-side. A client can be patched, so a client-side hasSGT boolean is worth nothing. The client's job is to collect a signature; the server verifies it and owns the result.