Keep status bar opaque in convergence mode

In mobile mode the status bar goes transparent when on the
homescreen so the wallpaper shows through. That is correct for
phone UX. In convergence/desktop mode it clashes with the always-
opaque dark dock: the top area looks light while the bottom is
dark. Return transparentBackground=false when convergence mode
is enabled so the panel stays consistently opaque.

containments/panel/qml/StatusPanel.qml

@@ -83,6 +83,12 @@ Item {
                 return true;
             }
 
+            // In convergence mode the status bar behaves like a desktop panel:
+            // always opaque so it matches the dock and doesn't let the wallpaper bleed through.
+            if (ShellSettings.Settings.convergenceModeEnabled) {
+                return false;
+            }
+
             return !containmentItem.showingApp && !containmentItem.fullscreen;
         }
         forcedComplementary: {