Enhance SL/TP calculation and order handling in LiveRegimeStrategy and OKXClient

- Updated `calculate_sl_tp` method to handle invalid entry prices and sides, returning (None, None) when necessary.
- Improved logging for SL/TP values in `LiveTradingBot` to display "N/A" for invalid values.
- Refined order placement in `OKXClient` to ensure guaranteed fill price retrieval, with fallback mechanisms for fetching order details and ticker prices if needed.
- Added error handling for scenarios where fill prices cannot be determined.

live_trading/live_regime_strategy.py

@@ -261,9 +261,9 @@ class LiveRegimeStrategy:
     
     def calculate_sl_tp(
         self,
-        entry_price: float,
+        entry_price: Optional[float],
         side: str
-    ) -> tuple[float, float]:
+    ) -> tuple[Optional[float], Optional[float]]:
         """
         Calculate stop-loss and take-profit prices.
         
@@ -272,10 +272,23 @@ class LiveRegimeStrategy:
             side: "long" or "short"
             
         Returns:
-            Tuple of (stop_loss_price, take_profit_price)
+            Tuple of (stop_loss_price, take_profit_price), or (None, None) if
+            entry_price is invalid
+            
+        Raises:
+            ValueError: If side is not "long" or "short"
         """
+        if entry_price is None or entry_price <= 0:
+            logger.error(
+                f"Invalid entry_price for SL/TP calculation: {entry_price}"
+            )
+            return None, None
+        
+        if side not in ("long", "short"):
+            raise ValueError(f"Invalid side: {side}. Must be 'long' or 'short'")
+        
         sl_pct = self.config.stop_loss_pct
-        tp_pct = self.config.take_profit_pct
+        tp_pct = self.config.take_profit_pct 
         
         if side == "long":
             stop_loss = entry_price * (1 - sl_pct)