Active tab highlight no longer sticks on non-tab routes

The dashboard header has a row of primary tabs (Boards, Stages, Settings). When you navigated to a route that was not one of those tabs — like a deep board detail — one of the tabs stayed highlighted as "active", which was visually confusing.

The highlight now clears when the route is not a tab, and reappears when you return to one. Small detail, but it makes the navigation feel less ambiguous.