Function app_menu_reactive 

pub fn app_menu_reactive(builder: impl Fn() -> Vec<MenuEntry> + 'static)

app_menu that re-lowers and re-installs whenever a locale-tracked read inside the builder changes — menu_role labels, res::str titles, and day::tr all read the locale signal, so a runtime language switch rebuilds the menu in the new language (docs/menus.md). Replacement drops the previous install’s action closures (context menus are unaffected). The binding lives in a root-owned scope: install once, at startup.