feat: 友链/书库/移动端导航/排行榜等多模块功能

新增模块：
- 友链（friendlink）后端处理 + 前端管理页与友链板
- 书库（library）：导入、章节、封面、阅读页、横竖版自适应 AdaptiveCoverSlot
- 顶栏导航（header_nav）配置与 MobileTabBar/MobileRailDrawers 移动端抽屉
- 排行榜 service 测试、站点页面测试、时间线发布（timeline_release）

其它改动：
- 后端 handlers/services 全量小幅调整
- 前端组件、库函数、URL/品牌/站点 URL 工具更新
- Lightbox 图片、MdEntries 条目卡、coverColor 派生色相等前端能力

frontend/package.json

@@ -7,10 +7,11 @@
     "build": "next build",
     "start": "next start -p 3000",
     "lint": "next lint",
-    "test": "node --experimental-strip-types --test lib/siteUrl.test.ts lib/jsonLd.test.ts lib/urlStyle.test.ts lib/widgetCode.test.ts lib/smartDiff.test.ts lib/dyEmoji.test.ts"
+    "test": "node --experimental-strip-types --test lib/siteUrl.test.ts lib/jsonLd.test.ts lib/urlStyle.test.ts lib/mobileTabs.test.ts lib/headerNav.test.ts lib/widgetCode.test.ts lib/smartDiff.test.ts lib/dyEmoji.test.ts lib/entryBlocks.test.ts"
   },
   "dependencies": {
     "hast-util-to-jsx-runtime": "^2.3.6",
+    "jszip": "^3.10.2",
     "lucide-react": "^0.460.0",
     "next": "^16.0.0",
     "react": "^19.0.0",
@@ -23,6 +24,7 @@
     "remark-parse": "^11.0.0",
     "remark-rehype": "^11.1.2",
     "shiki": "^4.4.3",
+    "turndown": "^7.2.4",
     "unified": "^11.0.5",
     "unist-util-visit": "^5.1.0"
   },
@@ -31,6 +33,7 @@
     "@types/node": "^22.0.0",
     "@types/react": "^19.0.0",
     "@types/react-dom": "^19.0.0",
+    "@types/turndown": "^5.0.6",
     "tailwindcss": "^4.0.0",
     "typescript": "^5.7.0"
   }