feat: PeopleLib 开放文献客户端，集成 Z-Library 与 LibGen 等多源检索

Electron 桌面客户端，聚合多个开放获取文献源的搜索、详情与下载。

新增数据源：
- Z-Library：邮箱登录（凭据本地存储），会话失效自动重登
- LibGen：适配新版 libgen.ac 前端（旧版 search.php 镜像已全部下线）
- Memory of the World、Sci-Hub、Anna's Archive

基础设施：
- mirror.js：镜像故障转移，支持串行优先与并发竞速两种策略，
  失效镜像 5 分钟冷却后自动重试，避免站点恢复后被永久跳过
- http.js：统一 15 秒请求超时，防止单个卡死镜像拖垮整次搜索
- settings.js：全局代理配置持久化，经 Electron net.fetch 生效于所有请求

Co-authored-by: factory-droid[bot] <138933559+factory-droid[bot]@users.noreply.github.com>

package.json

@@ -0,0 +1,36 @@
+{
+  "name": "peoplelib",
+  "version": "1.0.0",
+  "description": "开放获取文献与图书客户端（arXiv / Gutenberg / Open Library / DOAJ / PMC / bioRxiv / Standard Ebooks / Semantic Scholar / LibGen / Z-Library）",
+  "main": "main.js",
+  "author": "peoplelib",
+  "license": "MIT",
+  "scripts": {
+    "start": "electron .",
+    "portable": "node build-portable.js"
+  },
+  "dependencies": {
+    "undici": "^8.9.0"
+  },
+  "devDependencies": {
+    "electron": "^31.0.0"
+  },
+  "build": {
+    "appId": "com.peoplelib.client",
+    "productName": "PeopleLib",
+    "directories": {
+      "output": "dist"
+    },
+    "files": [
+      "main.js",
+      "preload.js",
+      "src/**/*"
+    ],
+    "win": {
+      "target": "portable"
+    },
+    "portable": {
+      "artifactName": "PeopleLib-${version}.exe"
+    }
+  }
+}