feat(web): keep deployed WebUI out of search-engine indexes

Searching "TsmusicBot" surfaced many deployed instances' WebUI URLs,
letting strangers walk into other people's control pages (issue #128).
Add defence-in-depth so crawlers stop indexing public deployments:

- send `X-Robots-Tag: noindex, nofollow` on every Express response
- serve `/robots.txt` with `User-agent: * / Disallow: /`
- add `<meta name="robots" content="noindex, nofollow">` to index.html,
  which also covers the /bot/<id> dedicated-link pages (same SPA shell)

These layers only prevent indexing; real protection stays with WebUI
auth and the reverse proxy. Document this in the README security section
and warn users not to post their WebUI link on public pages.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

README.md

@@ -891,6 +891,7 @@ A：本项目内置 `/login` 限流（每 IP 每分钟 5 次），但生产部
 - **会话存储**：服务端 SQLite 表 `sessions`，存储 sha256(token)；浏览器只持有原始 token cookie。7 天 TTL，每小时滚动续期。同账号最多 10 个并发会话（超出剔除最旧）。
 - **登录限流**：每 IP 每分钟 5 次 `/login` + 3 次 `/setup`，命中返回 429 + `Retry-After`。
 - **CSRF & 安全头**：所有 mutating 请求强制 `Origin`/`Referer` 同源；响应携带 `X-Frame-Options: DENY` 和 `Content-Security-Policy: frame-ancestors 'none'`（防点击劫持）。
+- **搜索引擎隐身（防止实例被收录，issue #128）**：为避免部署实例的 WebUI 被搜索引擎收录、被陌生人搜到控制页，采用纵深防御——所有响应携带 `X-Robots-Tag: noindex, nofollow`，`/robots.txt` 返回 `User-agent: * / Disallow: /`，`index.html` 内置 `<meta name="robots" content="noindex, nofollow">`（专属链接 `/bot/<id>` 等所有页面同样覆盖）。这些只阻止「被索引」，不是访问控制——**请不要把自己的 WebUI 链接发到公开网页 / 论坛 / 聊天群**，真正的防护来自登录鉴权与反向代理。
 - **配置变更**：反向代理部署务必 `"trustProxy": true`（详见 [反向代理部署注意事项](#反向代理部署注意事项)）。`config.adminGroups` 现已启用，用于限制管理类聊天命令只能由指定 TeamSpeak 服务器组运行（为空 = 不限制，详见 [TeamSpeak 命令权限](#teamspeak-命令权限管理类命令限制)）；`config.adminPassword` 仍为旧版预留字段，保留以兼容旧 `config.json`，当前未使用。
 
 ### v0.x — Bot Profile 自动更新与协议层升级

src/web/robots.test.ts

@@ -0,0 +1,86 @@
+import { describe, it, expect } from "vitest";
+import express from "express";
+import request from "supertest";
+import fs from "node:fs";
+import path from "node:path";
+import { fileURLToPath } from "node:url";
+
+/**
+ * Search-engine hardening for issue #128: searching "TsmusicBot" surfaced a
+ * large number of deployed instances' WebUI URLs, letting strangers walk into
+ * other people's control pages. The fix is defence in depth — none of these
+ * layers is authentication (that's handled elsewhere), they just keep the
+ * public URL out of crawler indexes:
+ *
+ *   1. `X-Robots-Tag: noindex, nofollow` on EVERY response;
+ *   2. `GET /robots.txt` → `User-agent: * / Disallow: /`;
+ *   3. `<meta name="robots" content="noindex, nofollow">` in web/index.html.
+ *
+ * The header middleware and the /robots.txt route both live at the top of
+ * `createWebServer` in `server.ts`; this test asserts the exact behaviour we
+ * expect from them in isolation (the wiring inside server.ts is verified by
+ * code review / git diff, matching security-headers.test.ts).
+ */
+describe("search-engine hardening (issue #128 noindex)", () => {
+  function buildApp() {
+    const app = express();
+    // Mirrors the security-headers middleware in server.ts.
+    app.use((_req, res, next) => {
+      res.setHeader("X-Frame-Options", "DENY");
+      res.setHeader("Content-Security-Policy", "frame-ancestors 'none'");
+      res.setHeader("X-Robots-Tag", "noindex, nofollow");
+      next();
+    });
+    // Mirrors the public /robots.txt route in server.ts.
+    app.get("/robots.txt", (_req, res) => {
+      res.type("text/plain").send("User-agent: *\nDisallow: /\n");
+    });
+    app.get("/", (_req, res) => res.json({ ok: true }));
+    app.post("/api/session/login", (_req, res) => res.json({ ok: true }));
+    return app;
+  }
+
+  it("sets X-Robots-Tag: noindex, nofollow on GET responses", async () => {
+    const res = await request(buildApp()).get("/");
+    expect(res.status).toBe(200);
+    expect(res.headers["x-robots-tag"]).toBe("noindex, nofollow");
+  });
+
+  it("sets X-Robots-Tag on POST (API) responses too", async () => {
+    const res = await request(buildApp()).post("/api/session/login");
+    expect(res.headers["x-robots-tag"]).toBe("noindex, nofollow");
+  });
+
+  it("serves /robots.txt disallowing all crawlers", async () => {
+    const res = await request(buildApp()).get("/robots.txt");
+    expect(res.status).toBe(200);
+    expect(res.headers["content-type"]).toMatch(/text\/plain/);
+    expect(res.text).toContain("User-agent: *");
+    expect(res.text).toContain("Disallow: /");
+  });
+
+  it("still tags the /robots.txt response itself as noindex", async () => {
+    const res = await request(buildApp()).get("/robots.txt");
+    expect(res.headers["x-robots-tag"]).toBe("noindex, nofollow");
+  });
+});
+
+describe("frontend robots meta tag (issue #128 noindex)", () => {
+  const indexHtmlPath = path.resolve(
+    path.dirname(fileURLToPath(import.meta.url)),
+    "../../web/index.html"
+  );
+  const html = fs.readFileSync(indexHtmlPath, "utf-8");
+
+  const robotsMeta = html.match(
+    /<meta\s+name=["']robots["']\s+content=["']([^"']+)["']\s*\/?>/i
+  );
+
+  it("declares a robots meta tag", () => {
+    expect(robotsMeta).not.toBeNull();
+  });
+
+  it("marks the SPA shell noindex, nofollow (covers /bot/<id> dedicated links)", () => {
+    expect(robotsMeta?.[1]).toBe("noindex, nofollow");
+  });
+});

src/web/server.ts

@@ -77,12 +77,19 @@ export function createWebServer(options: WebServerOptions): WebServer {
     app.set("trust proxy", true);
   }
 
-  // Security headers: prevent the WebUI from being embedded in a third-party
-  // iframe (clickjacking defence). CSP frame-ancestors is the modern equivalent
-  // of X-Frame-Options; both are set for compatibility across browsers.
+  // Security headers:
+  //  • X-Frame-Options / CSP frame-ancestors — prevent the WebUI from being
+  //    embedded in a third-party iframe (clickjacking defence). CSP
+  //    frame-ancestors is the modern equivalent of X-Frame-Options; both are
+  //    set for compatibility across browsers.
+  //  • X-Robots-Tag — keep deployed instances out of search-engine indexes
+  //    (issue #128: searching "TsmusicBot" surfaced strangers' WebUI URLs).
+  //    Set on EVERY response so JSON/API responses and the SPA shell are all
+  //    covered; complements /robots.txt and the <meta name="robots"> tag.
   app.use((_req, res, next) => {
     res.setHeader("X-Frame-Options", "DENY");
     res.setHeader("Content-Security-Policy", "frame-ancestors 'none'");
+    res.setHeader("X-Robots-Tag", "noindex, nofollow");
     next();
   });
 
@@ -95,6 +102,13 @@ export function createWebServer(options: WebServerOptions): WebServer {
   const permissions = createPermissionStore(options.database.db);
 
   // ─── Public routes (no auth, no CSRF) ───────────────────────────────────
+  // Disallow every crawler (issue #128). Declared before the static SPA
+  // fallback so this wins over index.html for /robots.txt. Belt-and-braces
+  // with the X-Robots-Tag header above and the <meta name="robots"> tag.
+  app.get("/robots.txt", (_req, res) => {
+    res.type("text/plain").send("User-agent: *\nDisallow: /\n");
+  });
+
   app.get("/api/health", (_req, res) => {
     res.json({ status: "ok", version: "0.1.0" });
   });

web/index.html

@@ -3,6 +3,12 @@
 <head>
   <meta charset="UTF-8">
   <meta name="viewport" content="width=device-width, initial-scale=1.0">
+  <!-- Keep deployed instances out of search-engine indexes (issue #128:
+       searching "TsmusicBot" surfaced strangers' WebUI URLs). Defence in depth
+       alongside the server's X-Robots-Tag header and /robots.txt. Applies to
+       the SPA shell and every in-app route (incl. /bot/<id> dedicated links),
+       since they all share this single index.html. -->
+  <meta name="robots" content="noindex, nofollow">
   <!-- Bilibili / NetEase / QQ image CDNs reject requests whose Referer is not on
        their whitelist, so we must not leak a Referer cross-origin. "same-origin"
        does exactly that: full Referer for our own requests, none for cross-origin