style(appShell): 优化应用外壳及底部导航样式与结构

- 在 tailwind 配置中添加应用外壳相关的 safelist 类名
- 替换 App.tsx 中应用外壳容器的类名，去除多余的内边距容器
- 在现代和遗留样式文件中新增移动端全屏、桌面居中列的样式规则
- 新增底部导航外层和内层的样式及响应式布局支持
- appShell.ts 中将样式类改为统一的 x8- 前缀类名
- BottomNav 组件使用新的样式类名以匹配样式调整
- Home 页面 ListRow 组件支持可选缩略图展示，增加界面展示丰富度

client/src/components/BottomNav.tsx

@@ -22,7 +22,7 @@ import {
 } from "lucide-react";
 import { Link, useLocation } from "wouter";
 import { useMemo } from "react";
-import { appShellColumnClass, appShellGutterClass } from "@/lib/appShell";
+import { bottomNavInnerClass, bottomNavOuterClass } from "@/lib/appShell";
 
 type BottomNavLocale = NonNullable<(typeof localeZh)["bottomNav"]>;
 
@@ -57,10 +57,10 @@ export default function BottomNav() {
 
   return (
     <nav
-      className={`fixed inset-x-0 bottom-0 z-50 flex justify-center pointer-events-none ${appShellGutterClass}`}
+      className={bottomNavOuterClass}
     >
       <div
-        className={`pointer-events-auto ${appShellColumnClass}`}
+        className={bottomNavInnerClass}
         style={{
           background: "rgba(10, 10, 12, 0.96)",
           backdropFilter: "blur(40px) saturate(200%)",