API
GET /api/player state, track, position, volume
POST /api/player/play|pause|toggle|stop|next|prev
POST /api/player/seek {"ms":90000}
POST /api/player/volume {"value":0-100} or {"delta":-5}
POST /api/player/source {"source":"spotify|hls|off|config"}
POST /api/player/url {"url":"https://…m3u8"} play a URL now
e.g. curl -X POST http://p4-aes67.local/api/player/next