fix: ::before backdrop was intercepting all clicks in NP overlay

The pseudo-element added for the flicker fix had position:absolute;inset:0
with no pointer-events:none, so it sat over the entire overlay and consumed
every click — queue items, lyrics lines, buttons. Add pointer-events:none.

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

styles.css

@@ -585,6 +585,7 @@ button:focus{outline:none}
   content:'';position:absolute;inset:0;
   background:var(--bg);z-index:-1;
   transform:translateZ(0);
+  pointer-events:none;
 }
 .np-overlay.open{transform:translate3d(0,0,0);-webkit-transform:translate3d(0,0,0)}