Get Fred Diagnostic

2026-08-26 (debugging the persistent RRPONTSYD/M2SL/WALCL HTTP 400 surfaced by the new Data Factory error tracking): AJ manually replicated the exact same request (same series_id, same api_key, same params) via his own browser and it succeeded -- meaning the request shape and the key value HE tested are both fine. Re-pasting the key into Railway's env var didn't clear the error either. This endpoint runs the IDENTICAL request server-side, from inside the actual Railway process, and returns FRED's real response instead of another layer of guessing. Never echoes the key itself -- only its length and whether it has leading/trailing whitespace (a very common real cause of this exact symptom: an invisible copy-paste artifact that works fine when a browser trims it but not when sent raw over HTTP), plus FRED's actual status code and response body for the RRPONTSYD call so we can see FRED's own error message text.