fix(ui): improve layout

[DarkGenius]

UI Layout Improvements

This pull request introduces several improvements to the UI layout, enhancing user experience and visual consistency.

Key Changes:

• Fixed Sidebar and Header: The main sidebar and the top header are now fixed in place. This ensures that navigation and search controls are always accessible, regardless of the page scroll position.
• Content Scrolling: The main content area is now the primary scrolling region, preventing the sidebar and header from scrolling out of view.
• Visual Alignment: The padding of the sidebar's logo section has been adjusted to ensure its bottom border aligns perfectly with the header's bottom border, creating a cleaner and more unified look.

[Dumbris]

Hey, @DarkGenius thank you for your contribution!
Could you rebase your PR branch on latest main? I have fixed e2e tests and pr-build workflows.

[Dumbris]

Solid improvement, thank you!