Fix command palette selection mismatch and card highlight z-index

Sort filtered items by group order so display indices match the array,
preventing wrong entity selection. Raise card-highlight z-index above
sticky section headers so the outline isn't clipped.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/wled_controller/static/css/layout.css

@@ -291,6 +291,8 @@ h2 {
     padding: 8px 16px;
     cursor: pointer;
     transition: background 0.1s;
+    position: relative;
+    z-index: 1;
 }
 
 .cp-result:hover {