fix(a11y): ink-400 对比度达标,接入 Noto Serif SC webfont,补纸张噪点与入场编排

- ink-400 #9C9587(2.90:1)→ #756F61(paper-50 4.87:1 / paper-100 4.55:1),正文级小字全部达标
- serif 栈插入 Noto Serif SC(fontsource 子集加载),Windows 不再跌进 SimSun
- 首页加 feTurbulence 纸张噪点层(.grain);报头/赛程行/预测版 rise-in 错峰入场(60ms 步进)
- reduce 动效用户:隐藏态与动画同在 no-preference 块,不会白屏
- Switch 提到模块顶层(修 render 重建丢焦点);a→Link(SPA 内链);h3→h2/h4→h3 修标题层级
- 按钮/输入热区抬高(btn 40px / btn-sm 32px / field py-2);index.css 硬编码色值改 :root 令牌

frontend/src/admin/AdminLayout.tsx

@@ -6,7 +6,7 @@
  */
 
 import { useState, useEffect, useCallback } from 'react'
-import { NavLink, Outlet, useLocation } from 'react-router-dom'
+import { NavLink, Link, Outlet, useLocation } from 'react-router-dom'
 import { fetchHealth } from './dal'
 
 const NAV_ITEMS = [
@@ -133,13 +133,13 @@ export default function AdminLayout() {
 
         {/* 底部 */}
         <div className="border-t border-ink-200 px-4 py-3">
-          <a
-            href="/"
+          <Link
+            to="/"
             className="flex min-h-[44px] items-center gap-2 text-xs text-ink-500 transition-colors hover:text-press"
           >
             <span aria-hidden="true">←</span>
             返回前台版面
-          </a>
+          </Link>
         </div>
       </aside>
 
@@ -170,13 +170,13 @@ export default function AdminLayout() {
               />
               {healthOk === null ? '检测中' : healthOk ? '系统正常' : '系统异常'}
             </span>
-            <a
-              href="/"
+            <Link
+              to="/"
               className="text-press transition-colors hover:text-press-dark sm:hidden"
               aria-label="返回前台"
             >
               前台
-            </a>
+            </Link>
           </div>
         </header>