Get Prediction Ledger

P1 of the Quant Research Factory roadmap (2026-08-10): surfaces services/prediction_ledger_service.py's accuracy scoreboard -- hit_rate_pct / avg_brier_score over every GRADED prediction, plus the most recent 50 rows (graded and pending) for spot-checking. Read-only, does not trigger a fresh grading pass (that runs on its own daily schedule via backend/main.py's APScheduler job) -- same fast/read-only pattern as get_security_scan() above. 2026-08-24: added source (e.g. "capital_flow_forecast" vs the default "direction_probability_service") now that more than one engine logs into this same table, so each can be scored on its own -- e.g. /admin/prediction-ledger?source=capital_flow_forecast to pull the real hit-rate/Brier numbers for a Capital Flow landing page.