A11y: Improved tagging of profile menu

- Swapped toggle out to actual button.
- Ensured menu items have proper menu item role.
- Added extra roles/labels where is makes sense.

resources/sass/_header.scss

@@ -65,6 +65,7 @@ header {
     margin: 0 (-(vars.$s));
     border-radius: 3px;
     gap: vars.$xs;
+    color: #FFF;
     > span {
       padding-inline-start: vars.$xs;
       display: inline-block;