feat: 公开商品页重设计 + web 上传修复 + 二维码配置

- 公开商品页（/product/:uuid）全面重设计：全宽正方形图片轮播、
  左右滑动切图、点击放大全屏查看、商品参数含描述、页脚贴底
- 修复 Flutter web 文件上传无反应（path→bytes）
- 修复 web 路由空白页（usePathUrlStrategy + 单层 MaterialApp.router）
- 二维码 URL 改为从 STORAGE_PUBLIC_URL 环境变量读取
- 新增 PUBLIC_URL dart-define → AppConfig.publicBaseUrl
- 新增 CI/CD workflows + NAS runner compose 配置
- seed S001 补充商品描述字段

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

client/lib/repositories/product_repository.dart

@@ -87,11 +87,16 @@ class ProductRepository {
     }
   }
 
-  Future<ProductImage> uploadImage(int productId, String filePath) async {
+  Future<ProductImage> uploadImage(int productId, String? filePath,
+      {Uint8List? bytes, String? fileName}) async {
     try {
-      final formData = FormData.fromMap({
-        'file': await MultipartFile.fromFile(filePath),
-      });
+      final MultipartFile file;
+      if (bytes != null) {
+        file = MultipartFile.fromBytes(bytes, filename: fileName ?? 'image.jpg');
+      } else {
+        file = await MultipartFile.fromFile(filePath!);
+      }
+      final formData = FormData.fromMap({'file': file});
       final resp = await _client.post('/products/$productId/images', data: formData);
       return ProductImage.fromJson(
           (resp.data as Map<String, dynamic>)['data'] as Map<String, dynamic>);