Hello ! I try to upgrade tailwindcss from v3 to v4 in my NextJS app but nothing work. First of all @tailwindcss/upgrade@next don't work (error: Cannot read properties of undefined (reading 'flatMap')). And using @tailwindcss/upgrade I have this first msg :

                                                                               
...
│ ↳ The configuration file at `./tailwind.config.js` could not be automatically migrated to the new CSS configuration format, so your CSS has been updated 
│   to load your existing configuration file. 
...
│ ↳ An error occurred while running `yarn remove postcss-import` 
│   yarn remove v1.22.22 
│   [1/2] Removing module postcss-import... 
│   info Visit https://yarnpkg.com/en/docs/cli/remove for documentation about this command. 
│   error This module isn't specified in a package.json file. 
...

And after all my sizing in my app are broken :