feat: 移除「关于本站」按钮与功能

- PublicLayout: 删除桌面导航/下拉菜单/页脚三处入口及空页脚,移除 about 导航类型与判断
- App: 移除 /about 路由及 AboutPage 引入
- 删除 pages/About 页面
- DocumentMeta: 移除 /about 的 meta 处理与 about 描述文案(中/英)
- i18n: 移除 aboutTitle / aboutIntro / footerAbout(中/英)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/i18n.tsx

@@ -122,10 +122,6 @@ const zhDict: Dict = {
   resourceLangFilter: "资料语言",
   filterTagClear: "清除标签",
   filterLanguageAll: "全部语言",
-  aboutTitle: "关于本站",
-  aboutIntro:
-    "ARK 数据库汇总官方教材、公告、视频与常用文件，帮助社区快速获取一致版本的可信内容。\n\n本站仅供展示与索引；权利归属以官方公告为准。",
-  footerAbout: "关于本站",
   footerAdminLogin: "管理员登录",
   adminSearchLogs: "搜索记录",
   adminMetricShares: "分享",
@@ -254,10 +250,6 @@ const enDict: Dict = {
   resourceLangFilter: "Resource language",
   filterTagClear: "Clear tag",
   filterLanguageAll: "All languages",
-  aboutTitle: "About this site",
-  aboutIntro:
-    "The ARK library brings together official decks, announcements, videos, and common files so the community can find consistent, trustworthy versions quickly.\n\nThis site is for discovery and indexing only; rights remain with official notices.",
-  footerAbout: "About",
   footerAdminLogin: "Admin sign-in",
   adminSearchLogs: "Search logs",
   adminMetricShares: "Shares",