music: 新建 music app，替换 piano-sheet

听歌 + 练琴曲目管理：
- 数据：piece (title/artist/category/lyrics/play_count/notes) + attachments (audio/video/pdf/image; image 带 role=chord/numbered/staff)
- 后端 axum + sqlite，附件流式落 PVC，ServeFile 支持 Range（视频拖动）
- 前端 guitar 风格 player：左 sidebar + tabs(歌词/吉他谱/简谱/五线谱/PDF/视频)，LRC 同步、快捷键、笔记自动保存
- ns cube-music + music.famzheng.me + bodylimit 5GiB
- scripts/import_guitar.py 用于把 oci /data/guitar/ 旧曲库导入

apps/music/Cargo.toml

@@ -0,0 +1,18 @@
+[package]
+name = "music"
+version = "0.1.0"
+edition.workspace = true
+license.workspace = true
+authors.workspace = true
+description = "music.famzheng.me — 听歌 + 练琴 曲目管理 (video / audio / pdf / png)"
+
+[dependencies]
+cube-core = { path = "../../crates/cube-core" }
+axum = { workspace = true, features = ["multipart"] }
+tokio = { workspace = true }
+tower = { workspace = true }
+tower-http = { workspace = true }
+tracing = { workspace = true }
+serde = { workspace = true }
+serde_json = { workspace = true }
+rusqlite = { workspace = true }