fix: karaoke button on its own row, separated from Prev/Random/Next

Karaoke toggle now spans full width of ring-header-controls grid,
pushing nav buttons (Prev/Random/Next) to their own 3-column row.
When karaoke is display:none (non-eligible shops), nav buttons
flow naturally into row 2. No template changes.

make_post_sell/static/css/common.css

@@ -2890,6 +2890,11 @@ textarea {
     align-items: center;
 }
 
+.ring-header-controls .ring-karaoke-btn {
+    grid-column: 1 / -1;
+    justify-self: end;
+}
+
 .skip-next-btn {
     font-size: 1.1em;
     padding: 12px 24px;