fix(app): remove redundant overflow hidden causing iOS sidebar scroll flicker

The inner sidebarContent had overflow: "hidden" while the parent
mobileSidebar already clips. On iOS, nested overflow clipping on
Animated.View with transforms and scroll containers causes rendering
artifacts during scroll.

packages/app/src/components/left-sidebar.tsx

@@ -811,7 +811,6 @@ const styles = StyleSheet.create((theme) => ({
   sidebarContent: {
     flex: 1,
     minHeight: 0,
-    overflow: "hidden",
   },
   desktopSidebar: {
     position: "relative",