Add risk management features: implement loss limits, trade limits, and pre-trade validation; update settings and tests

src/arbitrade/risk/__init__.py

@@ -0,0 +1,7 @@
+"""Risk management helpers."""
+
+from arbitrade.risk.loss_limits import LossLimitGuard
+from arbitrade.risk.pre_trade import PreTradeValidator
+from arbitrade.risk.trade_limits import TradeLimitsGuard
+
+__all__ = ["LossLimitGuard", "TradeLimitsGuard", "PreTradeValidator"]