Add wallet-level CheckProofState cleanup and Restore recovery (NUT-07, NUT-09)

[Amperstrand]

Problem

Client endpoints exist for CheckProofState (NUT-07) and Restore (NUT-09) but the Wallet type doesn't expose methods for:

1. Checking and cleaning up spent proofs
2. Recovering orphaned signatures after crash

Fix

• Wallet.CheckAndRemoveSpentProofs() — batch check proofs, delete SPENT ones
• Wallet.Restore() — regenerate blinded messages, batch restore (25/batch per Nutshell)

References

Nutshell Python: wallet.invalidate(), wallet.restore_tokens_for_keyset()

Discovered by

TollGate ecosystem audit (July 2026).

[Amperstrand]

Partially addressed

The wallet-level methods are not yet implemented in OpenTollGate/gonuts-tollgate, but the building blocks are in place:

• client.PostCheckProofState() exists (NUT-07)
• client.PostRestore() exists (NUT-09)

A standalone token recovery tool using these primitives has been built and tested: tollgate-module-basic-go PR #340 — it reads rejected tokens, checks proof state via NUT-07, and recovers unspent tokens via Wallet.Receive().

Adding convenience methods (Wallet.CheckAndRemoveSpentProofs() and Wallet.Restore()) is a future task, tracked separately.