The aggregated /api/v1/snapshot poll now emits a `scene_playlists` section
(each playlist with its `is_running` flag) plus a companion `playlist_state`
key carrying the single global cycling state (running playlist, current index/
preset, dwell) — so the HA-coordinator and other low-overhead pollers get
playlist state in the same round trip as scenes/targets, matching the other
entity sections. Gated by the `scene_playlists` include-section like the rest.
Reuses the existing list_scene_playlists handler; snapshot route tests updated.
alexei.dolgolyov
abc204c04e