fix: ensure arc60 data is always base64 encoded

[acfunk]

Pull Request Template

Description

• Fixing a bug where arc60 data is double base64 encoded.

Checklist

• [ X ] Have you tested your changes locally?
• [ X ] Have you reviewed the code for any potential issues?
• [ X ] Have you documented any necessary changes in the project's documentation?
• [ X ] Have you added any necessary tests for your changes?
• [ X ] Have you updated any relevant dependencies?

Additional Notes

• The build throws a warning warning Async method 'signArc60Data' has a complexity of 21. Maximum allowed is 20. If that is unacceptable, it will need to be refactored.

[wjbeau]

I cleaned this up more fully in #200. The arc60 path was not using the Transport classes at all (incorrectly) thus leading to confusion.