fix(about): bump displayed version to 1.9.0

Align about screen with pubspec.yaml.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: gitubpatrice

lib/screens/about_screen.dart

@@ -10,7 +10,7 @@ class AboutScreen extends StatefulWidget {
 }
 
 class _AboutScreenState extends State<AboutScreen> {
-  static const _version = '1.8.0';
+  static const _version = '1.9.0';
   static const _author = 'Patrice Haltaya';
 
   bool _checkingUpdate = false;