EMULSIF-565: Upgrade Emulsify UI Kit to Emulsify Core 4.x

[robherba]

Ticket(s):

• https://fourkitchens.clickup.com/t/36718269/EMULSIF-565
• https://fourkitchens.clickup.com/t/36718269/EMULSIF-252
• https://fourkitchens.clickup.com/t/36718269/EMULSIF-560

Summary

This PR upgrades the Emulsify UI Kit to Emulsify Core 4.x, replacing the legacy Webpack build with Vite and updating the project to Node 24.

Documentation update (required)

If this pull request requires a change to Emulsify documentation, those changes, updates, and/or new information must accompany this pull request.

How to review this pull request

1. Verify .nvmrc and package.json are configured to use Node 24.
2. Confirm @emulsify/core has been upgraded to 4.x, Webpack references have been removed, and Vite scripts are in place.
3. From a clean checkout, run:

   npm install
   npm run tokens:build
   npm run build

   Verify all commands complete successfully.
4. Run npm run storybook and verify Storybook starts correctly, existing UI Kit components render as expected, and token-generated styles are applied.
5. Run the following commands:

   npm run storybook-build
   npm run audit
   npm run audit:twig-stories
   npm run lint
   npm test
   npm run a11y

   Verify each command completes successfully, or document any existing unrelated issues.
6. Verify the visual regression workflow, CI, and deployment pipelines continue to work using Node 24 and the updated build commands.

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[mariannuar]

@robherba Thank you very much for doing this work. It looks and works great!!! I just saw that when running npm run lint, we are getting some errors:

Besides that, I don't have any feedback from my side. Great work!