chore(header): update background color and add border to enhance header styling for better visibility and consistency

Author: partyparrotgreg

apps/insights/src/components/Root/header.module.scss

@@ -4,7 +4,8 @@
   position: sticky;
   top: 0;
   width: 100%;
-  background-color: theme.color("background", "nav-blur");
+  background-color: theme.color("background", "primary");
+  border-bottom: 1px solid theme.color("background", "secondary");
   // TODO: This causes that navigation is not fixed
   // backdrop-filter: blur(32px);