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>

test-search.js

@@ -0,0 +1,111 @@
+// 临时测试脚本：完全模拟 main.js 的初始化流程，跑全部数据源搜索
+const { app, session } = require('electron');
+const path = require('path');
+
+app.setName('PeopleLib');
+app.commandLine.appendSwitch('ignore-certificate-errors');
+
+const userDataDir = path.join(app.getPath('appData'), 'PeopleLib');
+app.setPath('userData', userDataDir);
+
+const sources = require('./src/sources');
+const zlibAuth = require('./src/sources/zlib-auth');
+const settings = require('./src/settings');
+const { setProxy, getProxy } = require('./src/sources/http');
+
+zlibAuth.init(userDataDir);
+settings.init(userDataDir);
+
+// 允许通过命令行覆盖代理：electron test-search.js --proxy http://localhost:7897
+const argv = process.argv.slice(2);
+const pIdx = argv.indexOf('--proxy');
+const proxyOverride = pIdx >= 0 ? argv[pIdx + 1] : null;
+setProxy(proxyOverride !== null ? proxyOverride : settings.get('proxy', ''));
+
+function mask(s) {
+  s = String(s || '');
+  return s.length > 8 ? s.slice(0, 4) + '***' + s.slice(-2) : '***';
+}
+
+const CASES = [
+  { id: 'motw', kw: 'marx' },
+  { id: 'scihub', kw: '10.1038/nature12373' },
+  { id: 'libgen', kw: 'godel escher bach' },
+  { id: 'zlib', kw: 'godel' },
+  { id: 'gutenberg', kw: 'alice' },
+  { id: 'arxiv', kw: 'transformer' }
+];
+
+async function runCase(c) {
+  const label = `[${c.id}]`;
+  const t0 = Date.now();
+  try {
+    const src = sources.getSource(c.id);
+    const r = await src.search(c.kw, 1);
+    const n = (r.items || []).length;
+    console.log(`${label} search("${c.kw}") -> ${n} items, maxPage=${r.maxPage} (${Date.now() - t0}ms)`);
+    if (!n) {
+      console.log(`${label}   !! EMPTY RESULT`);
+      return { id: c.id, ok: false, reason: 'empty' };
+    }
+    for (const it of r.items.slice(0, 2)) {
+      console.log(`${label}   - ${String(it.title).slice(0, 70)} | ${String(it.subtitle || '').slice(0, 40)}`);
+    }
+    // 顺带验证 detail + download 链路
+    const first = r.items[0];
+    try {
+      const d = await src.detail(first.postId);
+      console.log(`${label}   detail OK: ${String(d.title).slice(0, 60)}`);
+    } catch (e) {
+      console.log(`${label}   detail FAIL: ${e.message}`);
+    }
+    try {
+      const dl = await src.download(first.postId);
+      const files = (dl.files || []).length;
+      const links = (dl.links || []).length;
+      console.log(`${label}   download OK: ${files} files, ${links} links`);
+      if (files) console.log(`${label}     file: ${dl.files[0].name} -> ${String(dl.files[0].link).slice(0, 80)}`);
+    } catch (e) {
+      console.log(`${label}   download FAIL: ${e.message}`);
+    }
+    return { id: c.id, ok: true, n };
+  } catch (e) {
+    console.log(`${label} SEARCH FAIL (${Date.now() - t0}ms): ${e.message}`);
+    return { id: c.id, ok: false, reason: e.message };
+  }
+}
+
+app.whenReady().then(async () => {
+  const p = getProxy();
+  console.log('=== 环境 ===');
+  console.log('userData:', userDataDir);
+  console.log('proxy(app):', p || '(空 -> 使用系统代理)');
+  if (p) {
+    await session.defaultSession.setProxy({ proxyRules: p }).catch(() => {});
+  }
+  app.on('certificate-error', (event, wc, url, err, cert, cb) => {
+    event.preventDefault();
+    cb(true);
+  });
+
+  const s = zlibAuth.getSession();
+  const creds = zlibAuth.read();
+  console.log('zlib creds:', creds && creds.email ? creds.email : '(无)');
+  console.log('zlib session:', s ? `userId=${s.userId} userKey=${mask(s.userKey)} mirror='${s.mirror}'` : '(无)');
+  console.log('');
+
+  const results = [];
+  for (const c of CASES) {
+    results.push(await runCase(c));
+    console.log('');
+  }
+
+  console.log('=== 汇总 ===');
+  for (const r of results) {
+    console.log(`${r.ok ? 'PASS' : 'FAIL'}  ${r.id}${r.ok ? ` (${r.n})` : ` - ${r.reason}`}`);
+  }
+  const after = zlibAuth.getSession();
+  console.log('');
+  console.log('zlib session after:', after ? `mirror='${after.mirror}'` : '(无)');
+  app.exit(0);
+});