feat: add IAttestationRegistry interface for Nitro attestation tracking

[zardozmonopoly]

Summary

Adds IAttestationRegistry.sol, a new interface for tracking verified AWS Nitro Enclave attestations on Base L2.

Motivation

The existing INitroEnclaveVerifier handles proof verification but lacks a standardized interface for querying historical attestation records. This interface fills that gap.

Changes

• Add IAttestationRegistry interface under interfaces/multiproof/tee/
• Defines registerAttestation, revokeAttestation, getAttestation and attestationCount functions
• Includes AttestationRegistered and AttestationRevoked events for on-chain auditability

Testing

Interface only — no logic changes. Implementation and tests to follow in a subsequent PR.

[cb-heimdall]

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