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>

pubspec.yaml

@@ -80,12 +80,19 @@ dev_dependencies:
   # rules and activating additional ones.
   flutter_lints: ^5.0.0
   json_serializable: ^6.9.5
+  flutter_launcher_icons: ^0.14.4
   # Generator wird über tool/generate_api_client.sh (Java-CLI) gefahren —
   # kein build_runner-Hook, daher kein openapi_generator-Paket nötig.
 
 # For information on the generic Dart part of this file, see the
 # following page: https://dart.dev/tools/pub/pubspec
 
+flutter_launcher_icons:
+  android: "launcher_icon"
+  ios: true
+  image_path: "assets/launch_icon.png"
+  min_sdk_android: 21
+
 # The following section is specific to Flutter packages.
 flutter: