fix(ui): restore bottom padding to divider section

- Change pt-3 back to py-3 on divider container
- Ensures bottom padding when Custom Accent section is collapsed
- Prevents divider from being cramped at bottom edge
- Now has 12px padding on both top and bottom of entire section

ui/desktop/src/components/GooseSidebar/ThemeSelector.tsx

@@ -216,7 +216,7 @@ export function ThemeSelector({
         />
       </div>
 
-      <div className={cn(!horizontal && 'px-3', 'pt-3 border-t border-border-default')}>
+      <div className={cn(!horizontal && 'px-3', 'py-3 border-t border-border-default')}>
         <div className="flex items-center justify-between mb-2">
           <div className="flex items-center gap-2">
             <Palette className="h-4 w-4 text-text-muted" />