iOS: ask for the background refresh as the app leaves, too (#421)

Build 5. The badge's refresh was requested only when the app came
forward; iOS asks for it as the app goes to the background. The
request made on coming forward stays. The timing is still iOS's.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

ios/Sources/App.swift

@@ -23,6 +23,12 @@ final class SceneDelegate: UIResponder, UIWindowSceneDelegate {
         self.window = window
     }
 
+    /// iOS wants the request made as the app leaves, with the user's last look at the list; the
+    /// one made on coming forward stays for a run that was cut short.
+    func sceneDidEnterBackground(_ scene: UIScene) {
+        Badge.scheduleBackgroundRefresh()
+    }
+
     func sceneDidBecomeActive(_ scene: UIScene) {
         Badge.requestPermission()
         Badge.scheduleBackgroundRefresh()