fix(qq-fm): guard FM start when offline + reset radar page on re-login [#88 review]

- startFm() now refuses with 'Bot is not connected to TeamSpeak' before mutating the
  queue, so POST /api/player/:id/fm can no longer wipe the queue and flip the bot into
  FM mode while disconnected (the !fm chat command already had this guard).
- The /fm route's success detection also treats 'not connected' as a failure so the
  toast type is correct.
- QQMusicProvider.setCookie() resets radarPage to 1 so a re-login with a different
  account no longer inherits the previous account's radar pagination cursor.

src/bot/instance.ts

@@ -747,6 +747,12 @@ export class BotInstance extends EventEmitter {
   }
 
   async startFm(provider: MusicProvider = this.neteaseProvider): Promise<string> {
+    // Match the !fm chat-command guard: refuse before mutating the queue when
+    // offline, so the web /fm route can't wipe the queue + flip into FM mode
+    // while nothing can actually play.
+    if (!this.connected) {
+      return "Bot is not connected to TeamSpeak";
+    }
     if (!provider.getPersonalFm) {
       return `Personal FM is not available for ${provider.platform}`;
     }

src/music/qq.ts

@@ -462,6 +462,9 @@ export class QQMusicProvider implements MusicProvider {
 
   setCookie(cookie: string): void {
     this.cookie = cookie;
+    // Reset radar pagination so a re-login (different account) starts from the
+    // first page rather than inheriting the previous account's cursor.
+    this.radarPage = 1;
   }
 
   getCookie(): string {

src/web/api/player.ts

@@ -97,7 +97,13 @@ export function createPlayerRouter(
           : "netease"
       );
       const message = await bot.startFm(provider);
-      res.json({ ok: !message.startsWith("No FM songs") && !message.includes("not available"), message });
+      res.json({
+        ok:
+          !message.startsWith("No FM songs") &&
+          !message.includes("not available") &&
+          !message.includes("not connected"),
+        message,
+      });
     } catch (err) {
       res.status(500).json({ error: (err as Error).message });
     }