simplified code across the app and consolidated duplicated helpers

lib/widget/async_actions/async_action_button.dart

@@ -32,20 +32,12 @@ class AsyncActionButton extends StatelessWidget {
     onError: onError,
     onSuccess: onSuccess,
     builder: (context, busy, handler) {
-      final spinner = AppProgressIndicator.small(
-        color: Theme.of(context).colorScheme.onPrimary,
-      );
-      final content = busy
-          ? Row(
-              mainAxisSize: MainAxisSize.min,
-              children: [spinner, const SizedBox(width: 8), child],
+      final lead = busy
+          ? AppProgressIndicator.small(
+              color: Theme.of(context).colorScheme.onPrimary,
             )
-          : (icon != null
-                ? Row(
-                    mainAxisSize: MainAxisSize.min,
-                    children: [Icon(icon), const SizedBox(width: 8), child],
-                  )
-                : child);
+          : (icon == null ? null : Icon(icon));
+      final content = lead == null ? child : _leadingLabel(lead, child);
       final button = ElevatedButton(
         onPressed: handler,
         style: style,