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/music/api-server.ts

@@ -42,16 +42,17 @@ export function createApiServerManager(
         logger.error({ err }, "Failed to start NetEase Cloud Music API");
       }
 
-      // QQ Music API — placeholder (requires separate setup)
+      // QQ Music API — auto-starts on port 3200 when imported
       try {
+        await import("@sansenjian/qq-music-api");
         logger.info(
           { port: options.qqMusicPort },
-          "QQ Music API: not bundled, skipping"
+          "QQ Music API started"
         );
       } catch (err) {
-        logger.warn(
+        logger.error(
           { err },
-          "QQ Music API not available"
+          "Failed to start QQ Music API"
         );
       }
     },