docs: set Storybook dark mode correctly when switching VitePress theme

[larsrickert]

The embedded Storybook component docs did not correctly switch to dark mode when the theme is toggled in VitePress.

Checklist

• The added / edited code has been documented with JSDoc
• All changes are documented in the documentation app (folder apps/docs)
• If a new component is added, at least one Playwright screenshot test is added
• A changeset is added with npx changeset add if your changes should be released as npm package (because they affect the library usage)

[changeset-bot]

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Latest commit: 95713ee

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