SwapWidget font CSS not included in build

When a React application with SwapWidget is built locally (and/or deployed on IPFS, example here), some fonts cannot be fetched as they are not included in the build.

It plays well when it's deployed to Vercel as it only throws warnings like these:

Failed to decode downloaded font: https://uni-widget-iframe.vercel.app/~@fontsource/inter/files/inter-latin-variable-wghtOnly-normal.woff2

...but the app bootstraps successfully.

However, when I build it locally and upload to IPFS, the mentioned warning becomes an error because the resource cannot be found and results with the error:

Refused to apply style from 'https://bafybeigj6vftgedsms27yfe3ebzhanqnhgrwxic5hug4457mysbka6w5iy.ipfs.dweb.link/~@fontsource/ibm-plex-mono/400.css' because its MIME type ('text/plain') is not a supported stylesheet MIME type, and strict MIME checking is enabled.

@zzmp, I've seen the previous attempt, but I still have this problem.

Start by reviewing the SwapWidget build path and previous pull request #3331, then reproduce a local build and IPFS deployment to inspect how font assets are referenced. Done means the built application includes or correctly serves the fonts without missing-resource or stylesheet MIME errors.