fix: set TrackFader spacing to 16px to match MasterFader

Both track and master faders now have consistent 16px margin-left.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

components/tracks/TrackFader.tsx

@@ -82,7 +82,7 @@ export function TrackFader({
   }, [isDragging, handleMouseMove, handleMouseUp]);
 
   return (
-    <div className={cn('flex gap-2', className)} style={{ marginLeft: '12px' }}>
+    <div className={cn('flex gap-2', className)} style={{ marginLeft: '16px' }}>
       {/* dB Labels (Left) */}
       <div className="flex flex-col justify-between text-[9px] font-mono text-muted-foreground py-1">
         <span>0</span>