[Enhancement] Toolbar and header visual changes

[jakobe]

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Describe the enhancement

UX has made some small visual changes to the toolbar on mobile + desktop (before and after scroll):

• Toolbar on mobile should always be xxl/56px (effectively reverts changes done in [Enhancement] Add dynamic toolbar height and refine layout #2219)
• Toolbar on desktop should always be xxxxxl/72px (new size should be added to sizes-ramp)
• Toolbar separator bottom-line should always be visible on desktop
  • Except when tab-navigation is used
• Toolbar background should be Kirby black + 1% transparent
  • Please note: the design specs shows a translucent toolbar, but as this has implications when using tab navigation, this change is postponed to [Enhancement] Translucent toolbar and tab navigation #3247
• Toolbar buttons should have 16px spacing on the right on mobile and 24px on desktop
  Please note: This enhancement will be implemented in a separate issue when we fix the spacing of toolbar action buttons and space available for toolbar title (is currently partly overlapped by toolbar buttons)

Describe the solution you'd like

Have you considered any alternatives?

Are there any additional context?

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