Hardcoded round(qty, 1) caused -1111 Precision errors for TRXUSDT and
DOGEUSDT (stepSize=1, requires integers). Now lazily loads quantityPrecision
and pricePrecision from Binance futures_exchange_info per symbol. SL/TP
prices also use symbol-specific precision instead of hardcoded 4 decimals.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
