fix: preserve home screen scroll position on back navigation

lib/mixins/tab_visibility_aware.dart

@@ -3,6 +3,6 @@
 /// Used by MainScreen to pause expensive work (e.g. animation tickers)
 /// when the screen's tab is no longer visible, and resume it when shown again.
 mixin TabVisibilityAware {
-  void onTabShown();
+  void onTabShown({bool scrollToTop = true});
   void onTabHidden();
 }