Fix UI Bug in Presenton

Presenton, my open-source PowerPoint generator (Python + React) at https://github.com/presenton/presenton, has run into a user-interface problem that makes the app frustrating to use. The logic behind slide creation, FastAPI endpoints, and data processing are all fine; the issue sits squarely in the React front end. You’ll be diving into the current code-base, pinpointing what is causing the UI to glitch, then delivering a clean, self-contained fix.

I’ve already reproduced the fault locally, so you’ll receive clear steps to trigger it. Once the bug is resolved, I also want a brief note in the README describing the change and any dependencies or commands added.

Deliverables
• Pull request that eliminates the UI defect without introducing regressions
• Concise README update documenting your fix and setup notes
• Confirmation that the interface works as expected after running `npm run build` and the standard Docker workflow

If you’re comfortable debugging a React front end that communicates with a Python/FastAPI back end, this should be a focused, quick win for both of us.