[REFACTOR] Twenty UI multi barrel (#11301)

# Introduction
closes https://github.com/twentyhq/core-team-issues/issues/591
Same than for `twenty-shared` made in
https://github.com/twentyhq/twenty/pull/11083.

## TODO
- [x] Manual migrate twenty-website twenty-ui imports

## What's next:
- Generate barrel and migration script factorization within own package
+ tests
- Refactoring using preconstruct ? TimeBox
- Lint circular dependencies
- Lint import from barrel and forbid them

### Preconstruct
We need custom rollup plugins addition, but preconstruct does not expose
its rollup configuration. It might be possible to handle this using the
babel overrides. But was a big tunnel.
We could give it a try afterwards ! ( allowing cjs interop and stuff
like that )
Stuck to vite lib app

Closed related PRs:
- https://github.com/twentyhq/twenty/pull/11294
- https://github.com/twentyhq/twenty/pull/11203

packages/twenty-ui/.storybook/preview.tsx

@@ -1,14 +1,9 @@
-import { useEffect } from 'react';
 import { ThemeProvider } from '@emotion/react';
 import { Preview } from '@storybook/react';
+import { THEME_DARK, THEME_LIGHT, ThemeContextProvider } from '@ui/theme';
+import { useEffect } from 'react';
 import { useDarkMode } from 'storybook-dark-mode';
 
-import {
-  THEME_DARK,
-  THEME_LIGHT,
-  ThemeContextProvider,
-} from '../src/theme/index';
-
 const preview: Preview = {
   decorators: [
     (Story) => {