Scaffold twenty-new-ui (#21236)

Scaffolds `twenty-new-ui`, the next-gen replacement for `twenty-ui`, on
**SCSS** Modules + **Base UI** (no Linaria).

- **Tooling**: Vite lib build, subpaths mirror twenty-ui, typed SCSS
Modules, Storybook + axe a11y, size-limit, Nx targets.
- **Theme**: single token source → nx generateTheme emits the CSS vars +
accessor; parity test asserts token-for-token match with twenty-ui.

Migrated a first `Toggle` component with its stories to allow
@charlesBochet to wire the new pixel-diff system.

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

package.json

@@ -52,6 +52,7 @@
       "packages/twenty-server",
       "packages/twenty-emails",
       "packages/twenty-ui",
+      "packages/twenty-new-ui",
       "packages/twenty-utils",
       "packages/twenty-zapier",
       "packages/twenty-website",