update voucher tab

lib/widgets/image_loader.dart

+import 'package:flutter/material.dart';
+
+Widget loadNetworkImage({
+  required String? url,
+  BoxFit fit = BoxFit.cover,
+  double? width,
+  double? height,
+  String placeholderAsset = 'assets/images/sample.png',
+}) {
+  if (url == null || url.isEmpty) {
+    return Image.asset(
+      placeholderAsset,
+      fit: fit,
+      width: width,
+      height: height,
+    );
+  }
+
+  return Image.network(
+    url,
+    fit: fit,
+    width: width,
+    height: height,
+    loadingBuilder: (context, child, loadingProgress) {
+      if (loadingProgress == null) return child;
+      return Center(
+        child: SizedBox(
+          width: 24,
+          height: 24,
+          child: CircularProgressIndicator(
+            strokeWidth: 2,
+            value: loadingProgress.expectedTotalBytes != null
+                ? loadingProgress.cumulativeBytesLoaded /
+                loadingProgress.expectedTotalBytes!
+                : null,
+          ),
+        ),
+      );
+    },
+    errorBuilder: (context, error, stackTrace) {
+      return Image.asset(
+        placeholderAsset,
+        fit: fit,
+        width: width,
+        height: height,
+      );
+    },
+  );
+}