feat(web): artist search, artist pages, and full-catalogue playback

Adds artist support for the NetEase and QQ providers plus the matching UI.

Backend:
- SearchResult gains `artists`; new optional MusicProvider methods
  getArtistDetail / getArtistSongs / getArtistAlbums / getArtistAllSongs.
- NetEase: /cloudsearch type=100 for artist search, /artists, /artist/songs,
  /artist/album and /artist/desc for the artist page.
- QQ: singer search rides along in the existing musicu.fcg batch
  (search_type=1); singer detail via music.web_singer_info_svr. QQ exposes no
  working singer-song paging endpoint, so the full catalogue is built from the
  hot 50 plus every album of the singer (album search filtered by singerMID,
  songs fetched per album, de-duplicated, cached for 10 minutes). A failed
  album sweep is never cached and degrades to the hot list.
- API: GET /api/music/artist/:id and POST /api/player/:botId/play-artist
  (player.control capability, guest flag playCollection); /search/all now
  aggregates artists too.

Frontend:
- Search history in localStorage (max 10, per platform, never shared between
  users), shown as a dropdown under the search box and as 最近搜索 chips.
- Artist row in the search results; new /artist/:id page (portrait, aliases,
  stats, description, top songs, album shelf) with 播放 / 随机播放, which queue
  the singer's whole catalogue.
- playArtist store action.

Tests cover the provider mappers, the new routes, the play-artist collector
(paging, de-duplication, 500-track cap), permission gating and the new views.

src/music/provider.ts

@@ -59,6 +59,34 @@ export interface Album {
   platform: Platform;
 }
 
+/** An artist / singer entity. Only sources with a real artist concept expose
+ *  these (NetEase, QQ); the others simply never return `SearchResult.artists`
+ *  and leave the optional provider methods unimplemented. */
+export interface Artist {
+  id: string;
+  name: string;
+  avatarUrl: string;
+  platform: Platform;
+  /** Alternate names / romanizations (NetEase alias, QQ other_name). */
+  aliases?: string[];
+  songCount?: number;
+  albumCount?: number;
+}
+
+export interface ArtistDetail extends Artist {
+  /** Short biography, when the source provides one. */
+  description?: string;
+}
+
+/** One page of an artist's COMPLETE catalogue (the "全部歌曲" list), as opposed
+ *  to `getArtistSongs`, which only ever returns the hot top-N. */
+export interface ArtistSongPage {
+  songs: Song[];
+  /** Total tracks the source reports for this artist (best effort). */
+  total: number;
+  hasMore: boolean;
+}
+
 export interface LyricLine {
   time: number; // seconds
   text: string;
@@ -69,6 +97,8 @@ export interface SearchResult {
   songs: Song[];
   playlists: Playlist[];
   albums: Album[];
+  /** Present only for sources with an artist entity (NetEase, QQ). */
+  artists?: Artist[];
 }
 
 export interface QrCodeResult {
@@ -108,4 +138,16 @@ export interface MusicProvider {
   getDailyRecommendSongs?(): Promise<Song[]>;
   getUserPlaylists?(): Promise<Playlist[]>;
   getPlaylistDetail?(playlistId: string): Promise<PlaylistDetail | null>;
+  getArtistDetail?(artistId: string): Promise<ArtistDetail | null>;
+  /** The artist's most popular tracks, best-first. */
+  getArtistSongs?(artistId: string, limit?: number): Promise<Song[]>;
+  /** One page of the artist's full catalogue, best-first. Sources that can only
+   *  expose a fixed top-N list leave this unimplemented (the route then 501s and
+   *  the web hides the "全部歌曲" section). */
+  getArtistAllSongs?(
+    artistId: string,
+    offset?: number,
+    limit?: number
+  ): Promise<ArtistSongPage>;
+  getArtistAlbums?(artistId: string, limit?: number): Promise<Album[]>;
 }