[confidential-mint-burn] Mint does not check for u64 supply overflows correctly (Neodyme L01)

[samkim-crypto]

The proofs while minting contain CiphertextCommitmentEqualityProof that asserts the new supply ciphertext belongs to a specific pedersen commitment, on which the u64 overflow-check is proven.

But that new-supply-ciphertext is fully arbitrary. You have to check it against the actual new supply, computed in-contract, similar to how transfer does it:

// Check that the computed available balance is consistent with what was
// actually used to generate the zkp on the client side.
if new_source_available_balance != proof_context.new_source_ciphertext {
    return Err(TokenError::ConfidentialTransferBalanceMismatch.into());
}

The impact of this missing is likely small, but the whole range-proof does nothing without this check.