Support EIP-6120

It's still in Review state, but what do you think?

> Before this EIP, when users sign transactions to spend their approved tokens, they trust the front-end code entirely to construct those transactions honestly and correctly. This puts them at great risk of phishing sites.
>
> The Universal Token Router function arguments can act as a manifest for users when signing a transaction. With the support from wallets, users can see and review their expected token behavior instead of blindly trusting the application contracts and front-end code. Phishing sites will be much easier to detect and avoid for users.

https://eips.ethereum.org/EIPS/eip-6120

Start by reading the EIP-6120 specification linked in the issue, then inspect the repository to locate the relevant wallet transaction-signing entry point. The issue names no files, tests, or implementation scope, so confirm the expected support surface with maintainers before starting. Done should mean the agreed EIP-6120 behavior is supported and covered by appropriate tests.

Written by the indexing model from the issue text.