Atlassian Settings page app bar navigation not responsive

The `Atlassian Settings` page AppBar shows all tabs in a horizontal row regardless of screen size, causing layout overflow and poor UX on smaller screens. On small screens, the toolbar lacks clear visual separation between navigation and controls.

**Expected behavior:**
- Large screens: all section tabs visible inline, save controls pinned to the right
- Small screens: single active section shown with prev/next arrow navigation, no overflow

Start by locating the Atlassian Settings page AppBar and reproducing it at large and small screen sizes. Compare the current tab row and toolbar controls with the stated expected behavior; done means inline tabs and right-pinned save controls on large screens, and one active section with previous/next navigation and no overflow on small screens.

Written by the indexing model from the issue text.