refactor: update to work with autogen v0.2.*

[janaka]

Folks new to AutoGen would benefit from this simpler version of the UI sample.

The more advanced version in the autogen repo is much harder to follow because of the number of layers and complexity of each abstraction. Even though this earlier version had the same number of layers, each layer is far simpler. Also, the instructions to run in the readme are simpler. This makes the whole thing easier to grok. It's

There's value in having both available.

Changes

• Update the app to working autogen v0.2.*
• Rebuild the frontend and commit.
• Improve README with dev guide.

[janaka]

@victordibia make sense to merge? 🙏🏾