I built an Android app with Google AI Studio. Can you help me review it?

I'm a self-taught developer from India. I build small Android utilities and offline games, and I use Google AI Studio to generate most of the code.

I'm asking for help. I don't have a team or a senior developer to review my work, so I'd like to ask the DEV community.

The app

Board Foot Calculator is a free lumber calculator for woodworkers, carpenters and timber traders.

• Board feet from thickness, width, length and quantity
• Cost estimate with a waste percentage
• A multi-board lumber bill with totals
• Unit converter (board feet, cubic feet, cubic meters, linear feet)
• Wood species reference
• An optional AI chat assistant for lumber questions

Google Play: https://play.google.com/store/apps/details?id=com.gagan.boardfootcalculator

How it was built

I described the screens and the calculations to Google AI Studio, let it generate the code, and then tested, fixed and published the app myself. I'm not hiding that. I'd rather be upfront about it, because I want feedback on what actually shipped.

What I'd like you to check

I can't judge all of this myself, so these are the places where I think an experienced developer will see problems that I miss:

1. Math and rounding. Are the board foot and unit conversion results correct? Try odd inputs: zero, very large numbers, decimals, fractions.
2. The AI assistant. Is the API key handled safely? I know a key inside an Android app can be extracted, so I'd like to know the right way to protect it.
3. Security and privacy. Are there permissions or data flows I should remove or fix? The Play Store data safety section says no data is collected, and I want that to be true.
4. Performance and battery. Does it feel slow on older phones?
5. UI and usability. Is anything confusing for someone standing in a lumber yard with dusty hands?
6. Code quality. If you see patterns in AI-generated Android code that I should clean up, tell me.

How to help

• Install the app and try to break it
• Leave a comment here with what you found, even if it's one line
• If you work with lumber, tell me what a real workflow needs (nominal vs actual sizes, metric input, saving projects)

I'll reply to every comment, fix what I can, and write a follow-up post about what I learned.

Why I'm doing this

I think AI tools let people like me ship things we couldn't build alone, but they also make it easy to ship mistakes. The honest way forward is to let other developers look at the result.

Thank you for reading. Any feedback, including harsh feedback, is welcome.

You can see my other apps on Google Play.