chore(branding): Launcher-Icon generiert (Android + iOS)

- flutter_launcher_icons ausgefuehrt: Android-Mipmaps 'launcher_icon' (hdpi-xxxhdpi) + kompletter iOS-AppIcon-Satz
- AndroidManifest android:icon -> @mipmap/launcher_icon (passend zur Config)
- remove_alpha_ios: true -> kein Alpha im iOS-Icon (App-Store-konform)

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

android/app/src/main/AndroidManifest.xml

@@ -17,7 +17,7 @@
     <application
         android:label="Holzleitner Auslieferung"
         android:name="${applicationName}"
-        android:icon="@mipmap/ic_launcher"
+        android:icon="@mipmap/launcher_icon"
         android:networkSecurityConfig="@xml/network_security_config">
         <activity
             android:name=".MainActivity"