feat: align shared app foundations

test/common/widgets/app_network_image_test.dart

@@ -0,0 +1,38 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:jinzhi_flutter_app/common/theme/jinzhi_theme.dart';
+import 'package:jinzhi_flutter_app/common/widgets/app_network_image.dart';
+import 'package:shadcn_ui/shadcn_ui.dart';
+
+void main() {
+  testWidgets('uses the standard fallback for an empty image URL', (
+    tester,
+  ) async {
+    await tester.pumpWidget(
+      ShadApp(
+        theme: ShadThemeData(colorScheme: jinzhiLightScheme),
+        home: const Scaffold(body: AppNetworkImage(imageUrl: '  ')),
+      ),
+    );
+
+    expect(find.byIcon(Icons.image_not_supported_outlined), findsOneWidget);
+  });
+
+  testWidgets('uses a supplied fallback for an empty image URL', (
+    tester,
+  ) async {
+    await tester.pumpWidget(
+      ShadApp(
+        theme: ShadThemeData(colorScheme: jinzhiLightScheme),
+        home: const Scaffold(
+          body: AppNetworkImage(
+            imageUrl: '',
+            errorWidget: Text('image unavailable'),
+          ),
+        ),
+      ),
+    );
+
+    expect(find.text('image unavailable'), findsOneWidget);
+  });
+}