Refactor role selection dropdown to use Material widget for improved styling and tap target size

b0esche_cloud/lib/widgets/organization_settings_dialog.dart

@@ -556,16 +556,17 @@ class _OrganizationSettingsDialogState
               data: Theme.of(context).copyWith(
                 splashFactory: NoSplash.splashFactory,
                 buttonTheme: ButtonThemeData(splashColor: Colors.transparent),
+                materialTapTargetSize: MaterialTapTargetSize.shrinkWrap,
+                highlightColor: Colors.transparent,
+                splashColor: Colors.transparent,
               ),
               child: DropdownButtonFormField<String>(
                 initialValue: selectedRole,
                 items: ['admin', 'member'].map((role) {
                   return DropdownMenuItem(
                     value: role,
-                    child: InkWell(
-                      splashFactory: NoSplash.splashFactory,
-                      highlightColor: Colors.transparent,
-                      splashColor: Colors.transparent,
+                    child: Material(
+                      type: MaterialType.transparency,
                       child: Text(role),
                     ),
                   );