Polished layout and icons

lib/data/appTheme.dart

@@ -12,7 +12,7 @@ class AppTheme extends ChangeNotifier {
   static ThemeModeDisplay getDisplayOptions(ThemeMode theme) {
     switch(theme) {
       case ThemeMode.system:
-        return ThemeModeDisplay(icon: Icons.auto_awesome, displayName: "Systemvorgabe");
+        return ThemeModeDisplay(icon: Icons.auto_fix_high_outlined, displayName: "Systemvorgabe");
 
       case ThemeMode.light:
         return ThemeModeDisplay(icon: Icons.dark_mode_outlined, displayName: "Hell");