feat(fm): let each web user link their own NetEase account for personal FM (#164)

With several people sharing one bot, personal FM always followed the one
account the bot was logged in with. Each signed-in (non-guest) web user
can now scan a QR code under Settings → 账户 to link their own NetEase
account; FM they start from the WebUI then comes from their account.

- user_music_cookies table (per user + platform, dropped with the user).
- NeteaseProvider.pollQrLogin returns the cookie without storing it, so
  a personal login can never replace the bot's shared account;
  checkQrCodeStatus is now built on it. withCookie gives a view bound to
  another account.
- /api/me/music/netease: status / qrcode / qrcode/status / unlink, acting
  only on req.user. The cookie never leaves the server.
- POST /api/player/:botId/fm uses the caller's linked account for
  NetEase. Songs still resolve through the shared provider when played.

TeamSpeak chat !fm keeps using the shared account: chat users are not
tied to web accounts.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/web/server.ts

@@ -19,6 +19,7 @@ import { createUsersRouter } from "./api/users.js";
 import { createAuditStore } from "../data/audit.js";
 import { createAuditRouter } from "./api/audit.js";
 import { createFavoritesRouter } from "./api/favorites.js";
+import { createPersonalMusicRouter } from "./api/personal-music.js";
 import { createSavedQueuesRouter } from "./api/saved-queues.js";
 import { createSpotifyRouter } from "./api/spotify.js";
 import type { SpotifyOAuth } from "../music/spotify/spotify-oauth.js";
@@ -203,6 +204,13 @@ export function createWebServer(options: WebServerOptions): WebServer {
     );
   }
   app.use("/api/favorites", requireNotGuest, createFavoritesRouter(options.database, logger));
+  // The caller's own NetEase login for their personal FM (#164). Guests share
+  // one anonymous identity, so they cannot link an account.
+  app.use(
+    "/api/me/music",
+    requireNotGuest,
+    createPersonalMusicRouter(options.database, options.neteaseProvider, logger),
+  );
   // Saved queues (Feature 1, #119). Members + admins only (requireNotGuest);
   // the router itself 403s every route unless savedQueuesEnabled is on.
   app.use(