Batch-query persisted end-of-day price rows

Returns persisted end-of-day price rows from the Wisesheets historical price store. Use period=latest for one row per ticker, period=last252d for trailing trading-day windows, or period=YYYY-MM-DD..YYYY-MM-DD for paginated date ranges. Values are returned as strings to preserve DECIMAL/BIGINT precision. Symbol scope is resolved per account: most accounts resolve SEC filers plus US-listed ETFs and see anything else in meta.unknownSymbols, while accounts provisioned for unrestricted scope may request any symbol in the price store and always receive an empty meta.unknownSymbols.