Quant: FRED macro data client

REST client for FRED macroeconomic data series.

Files: Omni/Fund/Data/Fred.hs

Deliverables:

• getSeries :: Text -> IO (Either ApiError [FredObs]) — fetch a FRED series
• getMultiple :: [Text] -> IO (Either ApiError (Map Text [FredObs])) — batch fetch
• FredObs type (date, value)
• Named constants for key series: T10Y2Y, M2SL, UNRATE, CPIAUCSL, FEDFUNDS, VIXCLS
• Local cache in /var/fund/quant/fred/ — JSONL per series
• Refresh logic (macro data updates monthly/weekly, not daily)

API key: Free, register at https://fred.stlouisfed.org/docs/api/api_key.html Store in pass as omni/quant/fred-api-key, add to provision-secrets.sh.