fix: simulation conditions now check properly from first iteration

The first price check was always skipped because last_price was None.
Now first iteration primes last_price, subsequent iterations check conditions.

src/backend/app/services/simulate/engine.py

@@ -69,10 +69,12 @@ class SimulateEngine:
                         current_volume = float(price_data.get("volume", 0))
 
                         if current_price > 0:
+                            # Only check conditions if we have a previous price to compare
+                            if self.last_price is not None:
                                 await self._check_conditions(
                                     current_price, current_volume, price_data
                                 )
-
+                            # Update last price AFTER checking (so next iteration has comparison data)
                             self.last_price = current_price
                             self.last_volume = current_volume