Get Playlist Stream Estimates

Return the latest weekly snapshot for a track when no query params are supplied, one requested snapshot via date, or all weekly snapshots in a since/until range. Each row describes a trailing 28-day estimate as of its snapshot date. Returns 404 when no matching snapshot exists — this table is populated incrementally, so a 404 here does not necessarily mean the track ID is invalid. The message distinguishes the two cases: an unfiltered request (no date/since/until) reports the track has no estimate computed yet at all, while a filtered request reports only that nothing matches the requested date or range (the track may still have estimates outside it).