feat: 进行功能分区方便后期维护

- 添加导航条目和分类数据模型
- 实现导航卡片网格展示
- 支持点击卡片打开链接
- 添加主题样式（渐变色、卡片阴影）
- 区分系统默认和自定义条目
- 添加分类统计信息"

frontend/web/manifest.json

@@ -1,12 +1,11 @@
 {
-    "name": "frontend",
-    "short_name": "frontend",
+    "name": "Suxing Nav",
+    "short_name": "Suxing Nav",
     "start_url": ".",
     "display": "standalone",
-    "background_color": "#0175C2",
-    "theme_color": "#0175C2",
-    "description": "A new Flutter project.",
-    "orientation": "portrait-primary",
+    "background_color": "#F7F9FB",
+    "theme_color": "#3B82F6",
+    "description": "极简导航站，把常用站点收进一个页面，随手可用。",
     "prefer_related_applications": false,
     "icons": [
         {