chore: 添加 macOS/Web 平台支持 + 修复编译错误 + 开发环境文档

- 修复 CardTheme → CardThemeData（Flutter 3.41 API 变更）
- 修复 finance_screen 缺少 FormDialog import
- 修复工具栏 Row overflow（添加横向滚动）
- flutter create --platforms=macos,web 生成平台配置
- 添加 docs/dev-setup.md：完整开发环境配置指南
  含 Go/Flutter/Docker 安装、已知 macOS 26 兼容问题及解决方案

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

client/test/widget_test.dart

@@ -0,0 +1,30 @@
+// This is a basic Flutter widget test.
+//
+// To perform an interaction with a widget in your test, use the WidgetTester
+// utility in the flutter_test package. For example, you can send tap and scroll
+// gestures. You can also use WidgetTester to find child widgets in the widget
+// tree, read text, and verify that the values of widget properties are correct.
+
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+import 'package:jiu_client/main.dart';
+
+void main() {
+  testWidgets('Counter increments smoke test', (WidgetTester tester) async {
+    // Build our app and trigger a frame.
+    await tester.pumpWidget(const MyApp());
+
+    // Verify that our counter starts at 0.
+    expect(find.text('0'), findsOneWidget);
+    expect(find.text('1'), findsNothing);
+
+    // Tap the '+' icon and trigger a frame.
+    await tester.tap(find.byIcon(Icons.add));
+    await tester.pump();
+
+    // Verify that our counter has incremented.
+    expect(find.text('0'), findsNothing);
+    expect(find.text('1'), findsOneWidget);
+  });
+}