Responsive design topbar: display user icon directly instead of using the three dots menu

When clicked on, the three dots menu only shows the clickable user icon on a small screen (same size as the three dots icon as well), meaning the three dots menu is pointless as it only shows one item and could be replaced by this same item.

Start at the responsive topbar implementation and run the portal at a small-screen width to reproduce the three-dots menu behavior shown in the issue. Replace that single-item menu presentation with the user icon directly, then verify the icon remains clickable and the topbar behaves correctly on small screens.

Written by the indexing model from the issue text.