feat(music): add Kugou (酷狗音乐) as a music source (#69)

Adds a self-contained Kugou provider (bilibili-style: direct API calls, no
embedded API server, no new npm dependency) plus full backend + WebUI wiring.

Provider (src/music/kugou.ts): search, song-url (with device registration),
lyrics (KRC decode), song detail, playlist, album, personal FM, QR login +
cookie persistence, and quality. Request signing / crypto / KRC decoding are
ported from the MIT-licensed MakcRe/KuGouMusicApi using Node's built-in
crypto and zlib (no third-party crypto packages).

Wiring: the "kugou" platform is threaded through the provider contract, queue,
play-history, bot instance/manager dispatch (getProviderFor + the -k command
flag), index/server composition, the music/player/auth routers (unified
/search/all, /quality, the platform coercions, QR login), the cookie store,
and the WebUI (search source tab + badge, SongCard badge, brand token, and a
Kugou QR/cookie login card in Settings).

Verified live during development: search, lyrics, and album playback resolve
correctly. NOT verifiable in CI (Kugou anti-bot blocks the build host's IP):
play-URL resolution, QR login, and VIP audio — these are built faithfully to
the reference and need end-to-end testing on a non-flagged IP / a Kugou
account. See the header comment in kugou.ts.

Includes src/music/kugou.test.ts (mappers + KRC→LRC). An adversarial review
pass fixed: pagination truncating on filtered counts, an ms/seconds duration
heuristic, dfid soft-fail caching, the /v5/url random-dfid fallback, the FM
body identity, and an unguarded nickname decode.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/music/kugou.test.ts

@@ -0,0 +1,100 @@
+import { describe, it, expect } from "vitest";
+import { mapKugouSong, mapKugouSongs, mapKugouAlbums, krcToLrc } from "./kugou.js";
+import { parseLyrics } from "./netease.js";
+
+describe("mapKugouSongs", () => {
+  it("maps the mobile-search song shape to a Song with platform 'kugou'", () => {
+    // Shape captured live from mobilecdn.kugou.com/api/v3/search/song.
+    const raw = {
+      hash: "B3A52A7A958BF0AED0EBFBA2E9A818B7",
+      album_audio_id: 32100650,
+      album_id: "966846",
+      songname: "晴天",
+      singername: "周杰伦",
+      duration: 269,
+    };
+    const [song] = mapKugouSongs([raw]);
+    expect(song.platform).toBe("kugou");
+    expect(song.name).toBe("晴天");
+    expect(song.artist).toBe("周杰伦");
+    expect(song.duration).toBe(269);
+    // The id must round-trip hash + album_audio_id + album_id so getSongUrl
+    // can resolve a stream from a search result.
+    expect(song.id).toBe("b3a52a7a958bf0aed0ebfba2e9a818b7|32100650|966846");
+  });
+
+  it("treats nested audio_info durations as milliseconds and flat search durations as seconds", () => {
+    // List endpoints: ms under audio_info.
+    expect(mapKugouSong({ audio_info: { hash: "abc", duration: 215000 } }).duration).toBe(215);
+    // Search endpoint: a long-form track's flat `duration` stays seconds (no /1000).
+    expect(mapKugouSong({ hash: "abc", songname: "x", duration: 10800 }).duration).toBe(10800);
+  });
+
+  it("falls back to splitting '歌手 - 歌名' from the filename", () => {
+    const song = mapKugouSong({ FileHash: "deadbeef", filename: "周杰伦 - 稻香", Duration: 200 });
+    expect(song.artist).toBe("周杰伦");
+    expect(song.name).toBe("稻香");
+  });
+
+  it("uses PascalCase fields from the gateway shape and skips entries with no hash", () => {
+    const songs = mapKugouSongs([
+      { FileHash: "aa", SongName: "n", SingerName: "s", MixSongID: 1, AlbumID: 2 },
+      { songname: "no hash" } as any,
+    ]);
+    expect(songs).toHaveLength(1);
+    expect(songs[0].id).toBe("aa|1|2");
+  });
+
+  it("returns [] for non-array input", () => {
+    expect(mapKugouSongs(undefined)).toEqual([]);
+  });
+
+  it("maps the NESTED album/playlist track shape (base + audio_info)", () => {
+    // Shape captured live from /album/songs (叶惠美).
+    const raw = {
+      base: { album_id: 966846, album_audio_id: 32100648, audio_name: "以父之名", author_name: "周杰伦" },
+      audio_info: { hash: "DBC0207490EB51153EF933EF5A7E98E4", duration: 342047 },
+    };
+    const [song] = mapKugouSongs([raw]);
+    expect(song.name).toBe("以父之名");
+    expect(song.artist).toBe("周杰伦");
+    expect(song.duration).toBe(342); // ms → s
+    expect(song.id).toBe("dbc0207490eb51153ef933ef5a7e98e4|32100648|966846");
+  });
+});
+
+describe("krcToLrc", () => {
+  it("converts KRC [startMs,durMs] line timestamps + strips word timings into parseable LRC", () => {
+    // Shape captured live from lyrics.kugou.com (周杰伦 - 晴天).
+    const krc = [
+      "[ti:晴天]",
+      "[ar:周杰伦]",
+      "[0,2250]<0,160,0>晴<160,160,0>天",
+      "[63000,1800]<0,200,0>故<200,200,0>事",
+    ].join("\n");
+    const lrc = krcToLrc(krc);
+    expect(lrc).toContain("[00:00.00]晴天");
+    expect(lrc).toContain("[01:03.00]故事");
+    expect(lrc).not.toMatch(/<\d+,\d+,\d+>/); // word timings stripped
+
+    // And the shared LRC parser must now actually produce timed lines.
+    const lines = parseLyrics(lrc);
+    expect(lines.length).toBe(2);
+    expect(lines[0]).toEqual({ time: 0, text: "晴天" });
+    expect(lines[1].time).toBe(63);
+    expect(lines[1].text).toBe("故事");
+  });
+});
+
+describe("mapKugouAlbums", () => {
+  it("maps album shape and normalises {size} covers to https", () => {
+    const [album] = mapKugouAlbums([
+      { album_id: 966846, album_name: "叶惠美", singername: "周杰伦", sizable_cover: "http://imge.kugou.com/x/{size}/abc.jpg", songcount: 11 },
+    ]);
+    expect(album.platform).toBe("kugou");
+    expect(album.id).toBe("966846");
+    expect(album.name).toBe("叶惠美");
+    expect(album.coverUrl).toBe("https://imge.kugou.com/x/240/abc.jpg");
+    expect(album.songCount).toBe(11);
+  });
+});