auth.go has a duplicate interface compliance check that masks a missing check for the ContractAccount type.
https://github.com/initia-labs/minievm/blob/0bc0c0f19de493c3c711f6f3d48e5befb0c48115/x/evm/types/auth.go#L13-L22
While this doesnt cause runtime issues, it means were missing compile-time verification that ContractAccount implements sdk.AccountI. This could allow interface implementation bugs to slip through if the ContractAccount type is modified in the future.
Replace the duplicate check with the missing ContractAccount verification:
