Api V2 Gex Regime-History Get

Stored per-session regime reads, most recent first.

The z-scores are RECOMPUTED here from each row's stored raw scores against the current full window, rather than served as written. A row written on day 12 was normalized against 11 sessions; one written on day 90 against 60. Serving those side by side would put a strip on screen whose bars are not comparable to each other — which is the one thing a history strip exists to make possible.