fix(player): 私人 FM 模式下点击下一首按钮可正常切歌

FM 播放列表只保留 1 首，原 _nextPlay 走到"顺序模式 + 最后一首"
分支只弹"列表已播完"提示，仅 audioService end 事件中拉取下一首
FM 的逻辑生效，导致用户手动点击下一首无效（issue #666）。

抽出 _nextFmPlay，_nextPlay 入口检测 isFmPlaying 直接路由到 FM
分支；MusicHook end 事件去掉重复的 FM 处理，统一走 nextPlayOnEnd。

src/renderer/hooks/MusicHook.ts

@@ -535,43 +535,12 @@ const setupAudioListeners = () => {
     if (getPlayerStore().playMode === 1) {
       // 单曲循环模式
       replayMusic();
-    } else if (getPlayerStore().isFmPlaying) {
-      // 私人FM模式：自动获取下一首
-      try {
-        const { getPersonalFM } = await import('@/api/home');
-        const res = await getPersonalFM();
-        const songs = res.data?.data;
-        if (Array.isArray(songs) && songs.length > 0) {
-          const song = songs[0];
-          const fmSong = {
-            id: song.id,
-            name: song.name,
-            picUrl: song.al?.picUrl || song.album?.picUrl,
-            ar: song.artists || song.ar,
-            al: song.al || song.album,
-            source: 'netease' as const,
-            song,
-            ...song,
-            playLoading: false
-          } as any;
-          const { usePlaylistStore } = await import('@/store/modules/playlist');
-          const playlistStore = usePlaylistStore();
-          playlistStore.setPlayList([fmSong], false, false);
-          getPlayerStore().isFmPlaying = true; // setPlayList 会清除，需重设
-          const { playTrack } = await import('@/services/playbackController');
-          await playTrack(fmSong, true);
-        } else {
-          getPlayerStore().setIsPlay(false);
-        }
-      } catch (error) {
-        console.error('FM自动播放下一首失败:', error);
-        getPlayerStore().setIsPlay(false);
-      }
-    } else {
-      // 顺序播放、列表循环、随机播放模式：歌曲自然结束
-      const { usePlaylistStore } = await import('@/store/modules/playlist');
-      usePlaylistStore().nextPlayOnEnd();
+      return;
     }
+
+    // 其他模式（FM/顺序/列表循环/随机）：交给 playlist store 路由
+    const { usePlaylistStore } = await import('@/store/modules/playlist');
+    usePlaylistStore().nextPlayOnEnd();
   });
 
   audioService.on('previoustrack', () => {