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>

web/src/components/SongCard.vue

@@ -3,7 +3,13 @@
     <div class="song-index">{{ index }}</div>
     <CoverArt :url="song.coverUrl" :size="36" :radius="6" />
     <div class="song-info">
-      <div class="song-name">{{ song.name }}</div>
+      <div class="song-name-row">
+        <span class="song-name">{{ song.name }}</span>
+        <span
+          class="platform-badge"
+          :class="song.platform === 'qq' ? 'badge-qq' : 'badge-netease'"
+        >{{ song.platform === 'qq' ? 'QQ' : '网易云' }}</span>
+      </div>
       <div class="song-artist">{{ song.artist }}</div>
     </div>
     <div class="song-album">{{ song.album }}</div>
@@ -73,6 +79,13 @@ function formatDuration(seconds: number): string {
   min-width: 0;
 }
 
+.song-name-row {
+  display: flex;
+  align-items: center;
+  gap: 6px;
+  min-width: 0;
+}
+
 .song-name {
   font-size: 14px;
   font-weight: 500;
@@ -81,6 +94,25 @@ function formatDuration(seconds: number): string {
   text-overflow: ellipsis;
 }
 
+.platform-badge {
+  flex-shrink: 0;
+  font-size: 10px;
+  font-weight: 600;
+  padding: 1px 5px;
+  border-radius: 3px;
+  line-height: 1.4;
+}
+
+.badge-netease {
+  background: rgba(232, 17, 35, 0.15);
+  color: #e81123;
+}
+
+.badge-qq {
+  background: rgba(18, 183, 106, 0.15);
+  color: #12b76a;
+}
+
 .song-artist {
   font-size: 12px;
   color: var(--text-secondary);