feat: add QQ Music API integration, Pinia home cache, and unified search

- Start @sansenjian/qq-music-api server via dynamic import in api-server.ts
- Rewrite QQ Music provider to use real API endpoints (getSearchByKey,
  getMusicPlay, getSongListDetail, getAlbumInfo, getLyric, etc.)
- Cache home page data (recommend playlists, daily songs, user playlists)
  in Pinia store with 5-minute TTL to avoid refetching on every mount
- Add unified /api/music/search/all endpoint that queries both Netease
  and QQ providers in parallel and returns merged results
- Remove platform toggle from Search.vue; search both platforms at once
- Add platform badge (网易云 / QQ) to SongCard component

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/types/qq-music-api.d.ts

@@ -0,0 +1 @@
+declare module "@sansenjian/qq-music-api";