Retrieve all steps and a budgeted cycle series together.

Fetches steps once and computes cycles from the same data, avoiding a double fetch when both are needed. Returns { steps: {...}, cycles: {...} }.

max_points bounds the cycle series only. Steps are returned complete whatever it says, and deliberately: the client resolves step-within-cycle filters against this table and builds its hover labels from it, so a decimated steps table would make the same filter select different rows at different plot widths. The cycle series is what gets drawn, and what a long-cycling test can make unbounded.