fix(ios): adopt the UIScene life cycle — 1.2.3 (27)

Build 26 was the first one made with the iOS 27 SDK, and UIKit stops apps
without the scene life cycle at launch on iOS 27 (TN3187). The scene
delegate only shows the FlutterEngine that AppDelegate starts with the
process, so a VoIP push in the background still finds the CallKit plugin
and a running Dart isolate when no scene is connected.

app/pubspec.yaml

@@ -1,7 +1,7 @@
 name: sepot
 description: "Šepot — Soukromý messenger s E2E šifrováním"
 publish_to: 'none'
-version: 1.2.3+26
+version: 1.2.3+27
 
 environment:
   sdk: ^3.10.8