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/lib/headerNav.test.ts

@@ -0,0 +1,78 @@
+import assert from "node:assert/strict";
+import { describe, it } from "node:test";
+import {
+  DEFAULT_HEADER_NAV,
+  HEADER_NAV_BUILTIN_KEYS,
+  isHeaderNavCustom,
+  normalizeHeaderNav,
+  type HeaderNavItem,
+} from "./headerNav.ts";
+
+describe("normalizeHeaderNav", () => {
+  it("缺行/非法输入回落内置默认三项", () => {
+    assert.deepEqual(normalizeHeaderNav(undefined), DEFAULT_HEADER_NAV);
+    assert.deepEqual(normalizeHeaderNav(null), DEFAULT_HEADER_NAV);
+    assert.deepEqual(normalizeHeaderNav("home"), DEFAULT_HEADER_NAV);
+  });
+
+  it("默认三项顺序与注册表一致", () => {
+    assert.equal(DEFAULT_HEADER_NAV.length, 3);
+    assert.deepEqual(
+      DEFAULT_HEADER_NAV.map((i) => (i.type === "builtin" ? i.key : "")),
+      [...HEADER_NAV_BUILTIN_KEYS],
+    );
+  });
+
+  it("显式空数组表示全部隐藏，不回落默认", () => {
+    assert.deepEqual(normalizeHeaderNav([]), []);
+  });
+
+  it("自定义顺序与内容原样保留", () => {
+    const items: HeaderNavItem[] = [
+      { type: "builtin", key: "library" },
+      { type: "custom", label: "关于", url: "/p/about", new_tab: false },
+      { type: "builtin", key: "home" },
+      { type: "custom", label: "官网", url: "https://example.com", new_tab: true },
+    ];
+    assert.deepEqual(normalizeHeaderNav(items), items);
+  });
+
+  it("内置 key 去空白/小写容错、重复去重", () => {
+    assert.deepEqual(
+      normalizeHeaderNav([
+        { type: "builtin", key: " HOME " },
+        { type: "builtin", key: "home" },
+        { type: "builtin", key: "library" },
+      ]),
+      [
+        { type: "builtin", key: "home" },
+        { type: "builtin", key: "library" },
+      ],
+    );
+  });
+
+  it("未知内置 key 与非法自定义项被剔除", () => {
+    assert.deepEqual(
+      normalizeHeaderNav([
+        { type: "builtin", key: "nope" },
+        { type: "custom", label: "", url: "/x" },
+        { type: "custom", label: "坏地址", url: "javascript:alert(1)" },
+        { type: "custom", label: "相对路径", url: "relative" },
+        { type: "weird", key: "home" },
+        { type: "custom", label: "合法", url: "/links" },
+      ]),
+      [{ type: "custom", label: "合法", url: "/links", new_tab: false }],
+    );
+  });
+
+  it("自定义外链 new_tab 缺省为 true，站内为 false", () => {
+    const got = normalizeHeaderNav([
+      { type: "custom", label: "外链", url: "https://example.com" },
+      { type: "custom", label: "站内", url: "/p/about" },
+    ]);
+    assert.equal(got.length, 2);
+    assert.ok(got.every(isHeaderNavCustom));
+    assert.equal((got[0] as { new_tab: boolean }).new_tab, true);
+    assert.equal((got[1] as { new_tab: boolean }).new_tab, false);
+  });
+});