Fix GTK CSS warnings and popover cleanup on widget destroy

Remove overflow property from .icon-rounded (not valid in GTK CSS).
Remove prefers-reduced-motion media query (not supported by GTK CSS
engine - reduced motion is handled by gtk-enable-animations setting).
Unparent PopoverMenu on widget destroy to prevent finalization warnings
when library view refreshes.

src/ui/library_view.rs

@@ -607,6 +607,12 @@ fn attach_context_menu(widget: &impl gtk::prelude::IsA<gtk::Widget>, menu_model:
     popover.set_parent(widget.as_ref());
     popover.set_has_arrow(false);
 
+    // Unparent the popover when the widget is destroyed to avoid GTK warnings
+    let popover_cleanup = popover.clone();
+    widget.as_ref().connect_destroy(move |_| {
+        popover_cleanup.unparent();
+    });
+
     // Right-click
     let click = gtk::GestureClick::new();
     click.set_button(3);