Basic import test of app.py to guard against formatting issues

[abhahn]

Motivation and Context

Adding a simple import of app.py in the tests to be sure that there are no fundamental code issues (such as syntax or indentation errors) that will cause the code to break.

Will add additional unit tests / E2E tests in a separate PR.

Description

Contribution Checklist

• [ ] I have built and tested the code locally and in a deployed app
• [ ] For frontend changes, I have pulled the latest code from main, built the frontend, and committed all static files.
• [ ] This is a change for all users of this app. No code or asset is specific to my use case or my organization.
• [ ] I didn't break any existing functionality :smile: