Lock fungible tokens on another's behalf with valid lock allowance

`LockToken` does not currently support locking fungible tokens unless the calling user is the owner.

https://github.com/GalaChain/sdk/blob/main/chaincode/src/locks/lockTokens.ts#L99C1-L104C6

```
// for initial support of fungible tokens, require owner to be the caller.
if (tokenInstanceKey.isFungible()) {
throw new NotImplementedError("LockToken is not supported for fungible tokens", {
instanceKey: tokenInstanceKey.toStringKey()
});
}
```

This issue tracks testing and adding support for this functionality.

Read chaincode/src/locks/lockTokens.ts around lines 99-104, starting with the current fungible-token guard and how lock allowances are represented or validated nearby. Add support for locking fungible tokens on another user's behalf when a valid lock allowance exists, and add tests covering the supported and rejected cases.

Written by the indexing model from the issue text.