Add base skeleton

moneymgr_mobile/lib/widgets/app_button.dart

@@ -0,0 +1,45 @@
+import 'package:flextras/flextras.dart';
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_gutter/flutter_gutter.dart';
+import 'package:flutter_hooks/flutter_hooks.dart';
+import 'package:moneymgr_mobile/utils/extensions.dart';
+import 'package:moneymgr_mobile/utils/hooks.dart';
+
+
+/// A button that shows a circular progress indicator when the [onPressed] callback
+/// is pending.
+class AppButton extends HookWidget {
+  const AppButton({
+    super.key,
+    required this.onPressed,
+    required this.label,
+  });
+
+  final AsyncCallback? onPressed;
+  final String label;
+
+  @override
+  Widget build(BuildContext context) {
+    final (:pending, :snapshot, hasError: _) = useAsyncTask();
+
+    return FilledButton(
+      onPressed: onPressed == null ? null : () => pending.value = onPressed!(),
+      child: SeparatedRow(
+        separatorBuilder: () => const GutterSmall(),
+        mainAxisAlignment: MainAxisAlignment.center,
+        children: [
+          if (snapshot.connectionState == ConnectionState.waiting)
+            SizedBox.square(
+              dimension: 12,
+              child: CircularProgressIndicator(
+                strokeWidth: 2,
+                color: context.colorScheme.onPrimary,
+              ),
+            ),
+          Text(label),
+        ],
+      ),
+    );
+  }
+}