Function repair_nonce_tracker_for_signer 

pub async fn repair_nonce_tracker_for_signer(
    db: &dyn NonceWriter,
    provider: &DynProvider,
    exchange_address: Address,
    signer_address: WalletAddress,
) -> Result<(), RsmSignerError>

Repairs the persisted next nonce for signer_address from on-chain state.

Scanning starts at the persisted next_nonce, or zero if no tracker exists, and advances while Exchange.isNonceUsed returns true. On success, both next_nonce and last_synced_nonce are persisted to the first unused nonce. Callers should serialize repairs per signer with normal signing startup.