jupyter/notebook ? reverse-engineered prompt

I want to build a web-based notebook application for interactive computing, kind of like a simplified, modern version of Jupyter.

The main feature should be a notebook interface that runs in the browser. Users need to be able to create cells, write code in them, and execute the code to see the output appear directly below the cell. It should look clean and feel responsive.

While it should definitely support Python, please design it to be language-agnostic from the start so it can handle different kernels in the future. For the architecture, let's use a Python backend, similar to how Jupyter Server works. For the frontend, go with a modern stack that can deliver a slick UI, maybe taking inspiration from the newer JupyterLab components. Just get the basic project structure set up so I can run it locally for development.