feat(hub): Music app client — album grid, flat list, persistent player

Implements the client half of docs/musicbay.md against MNP 0.8:

- music-app.js: album grid (grouped by artist -> album, from index-time
  artist/album fields) or flat folder view, per-group localStorage
  toggle like Videos. MusicBrainz (music_meta_req) is only looked up
  when a track has no embedded cover at all — well-tagged files never
  trigger a network call, unlike Videos where TMDB is unconditional.
  Reuses video-app.js's MediaThumb/LazyTile (now exported) rather than
  duplicating the chunk-path thumbnail decode + virtualization.
- music-player.js: the persistent player bar — queue, shuffle (Fisher-
  Yates, keeps the current track in place when toggled), repeat (off/
  all/one), volume (localStorage), prev/next, a one-track prefetch
  cache. No MSE, no node-side streaming: a track is downloaded and
  decrypted once via file-utils.js's pipelinedDownload, same chunk
  pipeline Files already uses, then played from a blob URL.
- group-page.js: owns musicQueue/musicbrainzConfig state and renders
  MusicPlayerBar outside the tab-switched area — deliberately, so
  playback survives navigating to Chat/Files, the same reasoning the
  video/preview modals are shell-owned rather than app-owned.
- apps.js: registers "music". transport.js: fetchMusicMeta (keyed by
  path, same reordering-hazard fix as fetchMediaMeta),
  setMusicbrainzConfig/setMusicbrainzEnabled (signed ops, mirroring
  TMDB's), and the three new ack handlers. group-settings.js: a
  MusicBrainz settings section (contact string, per-group toggle) —
  the existing Applications checklist already picks up "music" for
  free, per apps.md's own claim.
- icon.js: music/pause/skip-next/skip-prev/shuffle/repeat/volume,
  drawn in the same stroked style as the existing set.
- i18n: group.tab_music, the music.* and settings_node.musicbrainz_*
  keys, translated (not just copied) across all ten locales, Polish
  carrying full one/few/many/other plural forms for music.n_tracks.
- webapp.py's _ASSETS, test_hook_ordering.py's STATIC_FILES and
  test_transport_contracts.py's SPLIT_FILES gain the two new files.

Full suite (common + hub + node): 1116 passed, no regressions.
`npm run sync-ui` in meshbay-client confirmed both files copied.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KBi7ALLGfwcjBXt57yNMcy

1 files changed, 31 insertions, 0 deletions

diff --git a/packages/meshbay-hub/src/meshbay_hub/static/locales/zh-CN.js b/packages/meshbay-hub/src/meshbay_hub/static/locales/zh-CN.js
index 33a0e25..7e7676b 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/locales/zh-CN.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/locales/zh-CN.js
@@ -74,6 +74,7 @@ export default {
   'group.tab_files': '文件',
   'group.tab_chat': '聊天',
   'group.tab_video': '视频',
+  'group.tab_music': '音乐',
   'group.tab_members': '成员',
   'group.tab_settings': "设置",
   'members.danger_leave_hint': "您将无法再访问该群组的文件和聊天。",
@@ -169,6 +170,27 @@ export default {
   'video.search_no_results': '未找到匹配项。',
   'video.search_apply_hint': '将应用于当前归类在此标题下的所有文件。',
 
+  // 音乐
+  'music.mode_grid': '专辑',
+  'music.mode_flat': '平铺列表',
+  'music.empty': '未找到音乐。',
+  'music.unknown_album': '未知专辑',
+  'music.play_all': '全部播放',
+  'music.n_tracks': {
+    one: '{n} 首曲目',
+    other: '{n} 首曲目',
+  },
+  'music.err_transport': '传输未连接',
+  'music.player_play': '播放',
+  'music.player_pause': '暂停',
+  'music.player_prev': '上一首',
+  'music.player_next': '下一首',
+  'music.player_shuffle': '随机播放',
+  'music.player_repeat_off': '不重复',
+  'music.player_repeat_all': '全部重复',
+  'music.player_repeat_one': '单曲重复',
+  'music.player_volume': '音量',
+
   // LAN cast
   'cast.start': '投射到设备',
   'cast.stop': '停止投射',
@@ -584,6 +606,15 @@ export default {
   'settings_node.video_root_title': '视频根目录',
   'settings_node.video_root_hint': '该文件夹（或子文件夹）将作为此群组"视频"应用的入口。在选择之前，"视频"中不会显示任何内容，也不会执行任何 TMDB 查询。',
   'settings_node.video_root_none': '— 未选择 —',
+  'settings_node.musicbrainz_title': 'MusicBrainz 元数据',
+  'settings_node.musicbrainz_hint': '当曲目没有可用的内嵌封面时，允许音乐应用显示来自 MusicBrainz 的封面和规范名称。关闭表示仅按标签/文件名浏览，不向第三方发送请求。',
+  'settings_node.musicbrainz_enabled': '已启用',
+  'settings_node.musicbrainz_disabled': '已禁用',
+  'settings_node.musicbrainz_contact_label': '联系方式（MusicBrainz 需要它才能响应请求）',
+  'settings_node.musicbrainz_contact_placeholder': 'you@example.com 或项目 URL',
+  'settings_node.musicbrainz_contact_set': '已配置联系方式。',
+  'settings_node.musicbrainz_contact_unset': '未配置联系方式 — 在设置之前，MusicBrainz 查询将保持关闭。',
+  'settings_node.musicbrainz_save': '保存',
   'settings_node.video_root_save': '保存',
   'settings_node.video_root_change_confirm': '更改视频根目录会替换每位成员在"视频"标签页中看到的内容。是否继续？',