feat(ssr): 真 SSR 收尾——干净 hydration 与浏览器原生滚动恢复

- 修复 onRenderClient 引入 serverClient 导致浏览器 process is not defined：
  抽出双端安全的 ssr/feedSeed.ts 作为唯一数据播种入口，serverClient 加 SSR 守卫
- 修复 React 19 Fizz Suspense Outlining：Suspense 边界从布局 Outlet 下移到
  各懒加载路由，SSR 输出不再出现 <!--$?--> / $RB / template 探针标记
- 修复窄屏 React #418 hydration 致命错误：useMediaQuery 首帧恒 false，
  useLayoutEffect 绘制前同步真实值；主题改 cookie 存储供 SSR 直出，
  head 内联防闪烁/缩放脚本移除（缩放锁改为客户端 zoomGuard 模块）
- 清理假 SSR 残留：删除 StaticFeedList 镜像组件、SSR 图标生成脚本、
  探针与死代码；列表接口裁剪正文，仅下发 excerpt/first_image
- Feed 与帖子详情改为窗口滚动（app-shell--doc-scroll）：删除虚拟列表、
  自研滚动快照与全局滚轮 hack；F5/前进后退滚动位置全部交给浏览器原生
  历史恢复，HTML 响应头 no-cache 配合；锚点/楼层用 scrollIntoView +
  scroll-margin-top 适配 sticky 顶栏

frontend/package-lock.json

@@ -21,7 +21,6 @@
         "@svg-maps/china": "^2.0.0",
         "@svg-maps/world": "^2.0.0",
         "@tailwindcss/vite": "^4.3.3",
-        "@tanstack/react-virtual": "^3.11.2",
         "@tiptap/core": "^3.26.1",
         "@tiptap/extension-code-block": "^3.26.1",
         "@tiptap/extension-image": "^3.26.1",
@@ -3119,33 +3118,6 @@
         "vite": "^5.2.0 || ^6 || ^7 || ^8"
       }
     },
-    "node_modules/@tanstack/react-virtual": {
-      "version": "3.14.2",
-      "resolved": "https://registry.npmjs.org/@tanstack/react-virtual/-/react-virtual-3.14.2.tgz",
-      "integrity": "sha512-IpWnmCLvuymRfeeLNVXIzNEYBFLpd3drVIS91sqV78VTZFyldlChkOocZRCPp1B+Wnk09bcLNme8WaMU/9/9bQ==",
-      "license": "MIT",
-      "dependencies": {
-        "@tanstack/virtual-core": "3.17.0"
-      },
-      "funding": {
-        "type": "github",
-        "url": "https://github.com/sponsors/tannerlinsley"
-      },
-      "peerDependencies": {
-        "react": "^16.8.0 || ^17.0.0 || ^18.0.0 || ^19.0.0",
-        "react-dom": "^16.8.0 || ^17.0.0 || ^18.0.0 || ^19.0.0"
-      }
-    },
-    "node_modules/@tanstack/virtual-core": {
-      "version": "3.17.0",
-      "resolved": "https://registry.npmjs.org/@tanstack/virtual-core/-/virtual-core-3.17.0.tgz",
-      "integrity": "sha512-gOxY/hFkPh/XQYhnThBHzkbkX3Ed+z/iushyz+R+JAr213aXxUDgQoTgTdrDpBSRsjFM73P/KfUyWmaF9WHMkQ==",
-      "license": "MIT",
-      "funding": {
-        "type": "github",
-        "url": "https://github.com/sponsors/tannerlinsley"
-      }
-    },
     "node_modules/@tiptap/core": {
       "version": "3.26.1",
       "resolved": "https://registry.npmjs.org/@tiptap/core/-/core-3.26.1.tgz",