style: format backtesting files with black

app/services/backtesting/ui_service.py

@@ -323,7 +323,7 @@ class BacktestPageService:
             margin_call_ltv=normalized_inputs.margin_call_ltv,
         )
 
-        # CRITICAL: The backtest engine uses a fixture provider (synthetic_v1), 
+        # CRITICAL: The backtest engine uses a fixture provider (synthetic_v1),
         # regardless of the data_source used for price fetching.
         # We must use the fixture provider's ID for the scenario, not the data source's ID.
         # The data_source parameter only affects price data fetching, not the backtest engine.