fix: make 'skip to content' consistent

[arbirali]

Description

This PR makes the "Skip to content" link styling to ensure a consistent and accessible experience across all pages.
The update applies unified SCSS rules for the .sr-only-focusable class within the header element, ensuring the link is:

• Positioned consistently at the top center of the page
• Clearly visible on focus with high contrast (black background, white text)
• Readable and easily accessible for keyboard users

Taiga Task (if you have access):

• Skip to main content

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Screenshots

Before	After