fix: CSS missing after build

[sapphi-red]

Vite expects each chunk in the bundle has a different preliminaryFileName here.
https://github.com/vitejs/vite/blob/cc980feb556bda324f1da7162a571150fcbaebed/packages/vite/src/node/plugins/css.ts#L781-L785
preliminaryFileName matches the value of fileName in renderChunk hook and fileName is unique in that hook, therefore preliminaryFileName should be unique.

https://discordapp.com/channels/804011606160703521/831456449632534538/1175056771384086651

[brc-dd]

Thanks 🙏