feat: add nonce and expiry to transfer attestations

[devv-leo]

Closes #561

Summary

Add nonce and expiry to transfer_with_attestation to prevent attestation replay. Nonces are per-signer (keyed by from address) and monotonically consumed.

Changes

Contract (src/lib.rs)

• Add AttestationNonceUsed(Address, u64) variant to DataKey2
• Extend transfer_with_attestation with attest_hash, network_id, nonce, expires_at
• Add network ID validation (NetworkIdMismatch if mismatch)
• Add nonce/expiry validation (SignatureExpired, SignatureReplay)
• Add dual-party auth (from.require_auth, to.require_auth)
• Add offering freeze, blacklist, whitelist, jurisdiction enforcement
• Nonce consumed only after all guards pass (prevents DoS)
• Event payload now includes nonce and expires_at
• atomic_swap passes expires_at=0 to skip nonce check

Tests

• All existing calls updated with nonce/expiry params
• New tests: expired_attestation_rejected, replayed_attestation_nonce_rejected, nonce_is_per_signer, attestation_used_at_exact_expiry
• Self-transfer test updated to match no-op behavior

Security

• Nonce validated early, consumed only after state mutation succeeds
• Per-signer scoping: nonces tracked per (from, nonce) pair
• Expired attestations rejected with SignatureExpired (error 27)
• Replayed nonces rejected with SignatureReplay (error 28)
• atomic_swap uses expires_at=0 sentinel to bypass attestation requirements

[drips-wave]

@devv-leo Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits