chore(branding): Anzeigename 'Holzleitner Auslieferung' + Launcher-Icon

- Android android:label, iOS CFBundleDisplayName, MaterialApp.title -> 'Holzleitner Auslieferung'
- flutter_launcher_icons (assets/launch_icon.png) als Dev-Dep + Config

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/widget/app.dart

@@ -120,6 +120,7 @@ class _DeliveryAppState extends State<DeliveryApp> {
               ),
             ],
             child: MaterialApp(
+              title: 'Holzleitner Auslieferung',
               // Wrap the Navigator (not just the home route) so the loading
               // overlay covers every pushed route — DeliveryDetail, Cars,
               // dialogs, etc. — not only the initial home tree.
@@ -153,6 +154,7 @@ class _DeliveryAppState extends State<DeliveryApp> {
 
         if (state is AppConfigLoadingFailed) {
           return MaterialApp(
+            title: 'Holzleitner Auslieferung',
             home: Scaffold(
               body: Center(child: Text("Fehler beim Laden der Konfiguration")),
             ),
@@ -160,6 +162,7 @@ class _DeliveryAppState extends State<DeliveryApp> {
         }
 
         return MaterialApp(
+          title: 'Holzleitner Auslieferung',
           home: Scaffold(
             body: Center(child: const CircularProgressIndicator()),
           ),