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/package-lock.json

@@ -8,6 +8,7 @@
       "name": "profeto-frontend",
       "version": "0.1.0",
       "dependencies": {
+        "@fontsource/noto-serif-sc": "^5.3.0",
         "react": "^18.3.1",
         "react-dom": "^18.3.1",
         "react-router-dom": "^6.30.6"
@@ -709,6 +710,15 @@
         "node": ">=12"
       }
     },
+    "node_modules/@fontsource/noto-serif-sc": {
+      "version": "5.3.0",
+      "resolved": "https://registry.npmmirror.com/@fontsource/noto-serif-sc/-/noto-serif-sc-5.3.0.tgz",
+      "integrity": "sha512-0/zaEFkidiWldE62rTeD74x8ygUsQvejiSNtO0LQxQk3qpaHnlMZ3w4C7yH80B4KTIg8VKeFP4oSgwWMchY9+g==",
+      "license": "OFL-1.1",
+      "funding": {
+        "url": "https://github.com/sponsors/ayuhito"
+      }
+    },
     "node_modules/@jridgewell/gen-mapping": {
       "version": "0.3.13",
       "resolved": "https://registry.npmjs.org/@jridgewell/gen-mapping/-/gen-mapping-0.3.13.tgz",