feat: 扫码商品详情页重设计 + 宣传主页 + nginx 路由完善

- public_product_screen: 1:1 复刻设计稿，新增商品介绍、批次防伪（自定义圆形印章）、完整商品参数表、门店营业时间、页脚链接
- app_theme: 完整品牌色系（brand/gray/accent/semantic）
- shop model: 新增 business_hours 字段，public 接口同步返回
- nginx: 新增 /product/ → Flutter app 扫码入口，修复 /docs /download html 后缀兼容
- web/: 新增宣传主页、功能页、文档页、扫码 HTML 及设计资源
- app_shell: 界面优化

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

client/web/manifest.json

@@ -1,11 +1,11 @@
 {
-    "name": "jiu_client",
-    "short_name": "jiu_client",
+    "name": "岩美",
+    "short_name": "岩美",
     "start_url": ".",
     "display": "standalone",
-    "background_color": "#0175C2",
-    "theme_color": "#0175C2",
-    "description": "A new Flutter project.",
+    "background_color": "#2563AC",
+    "theme_color": "#2563AC",
+    "description": "岩美酒库管理系统 — 酒店饮品库存与采购管理平台",
     "orientation": "portrait-primary",
     "prefer_related_applications": false,
     "icons": [