Fix header app name clickability issue, fix #12165

Signed-off-by: Jan-Christoph Borchardt <hey@jancborchardt.net>

core/css/header.scss

@@ -561,6 +561,7 @@ nav[role='navigation'] {
 			span {
 				opacity: .6;
 				bottom: 2px;
+				z-index: -1; /* fix clickability issue - otherwise we need to move the span into the link */
 			}
 
 			/* Prominent app title for current and hovered/focused app */