Per-master-key spend with previous-window comparison plus a full-slice summary (not limited by limit).
Success data: window, previousWindow, summary, rows (camelCase spend fields, spendChangePercent may be null).
Optional filters: departmentId (UUID) scopes slice; invalid UUID → 400 / 40013.
Optional. Bearer JWT, Virtual Key, or PAT. Server also accepts Cookie alephant_token; not modeled as a header here.
Optional in the spec; required for authenticated analytics. Omit for unauthenticated GET /v1/analytics/health.
Calendar preset; default 30d.
YYYY-MM-DD with end.
YYYY-MM-DD with start.
Max keys returned (default 200, max 200).
Optional department UUID filter; must be valid if non-empty.
