CVE-2026-55764: klever-go: SFT add-quantity `int64` overflow bypasses a finite per-nonce MaxSupply

On the SFT add-quantity path the only supply bound is SFTAddCirculation, which does meta.Circulation += amount with no overflow guard, then checks if meta.Circulation > meta.MaxSupply && meta.MaxSupply != 0. If amount overflows int64 and wraps negative, negative > MaxSupply is false, the cap check passes, the function returns nil, and the balance credit stands. A nonce created with a finite MaxSupply (e.g. 1000) can thus be minted to ~MaxInt64 tokens in one transaction. The fungible mint path is not vulnerable — it has a post-increment MintedValue <= 0 guard that the SFT path lacks.