[bug]: Fix dark mode and implement a11y tests for dark mode

[oliverschuerch]

Depandant on:

• feat(tokens , styles): palettes 2.0 #5250

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Fix the header and the footer in dark mode.

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Dark mode a11y e2e tests have been deactivated, because the dark mode design is not working correctly...
Reactivate the tests as soon as the component has been fixed in that regard.

To do so, remove the filter option from all the scheme() functions in the footer.snapshot.stories.ts file.

[gfellerph]

Maybe adding data-color-scheme="light" to the footer will fix the issue until it has dark mode tokens.