Add FastAPI backend for energy trading system

Implements FastAPI backend with ML model support for energy trading,
including price prediction models and RL-based battery trading policy.
Features dashboard, trading, backtest, and settings API routes with
WebSocket support for real-time updates.

backend/app/ml/features/regional_features.py

@@ -0,0 +1,18 @@
+from typing import List
+import pandas as pd
+
+
+def add_regional_features(df: pd.DataFrame, regions: List[str]) -> pd.DataFrame:
+    result = df.copy()
+
+    if "region" in result.columns and "real_time_price" in result.columns:
+        avg_price_by_region = result.groupby("region")["real_time_price"].mean()
+
+        for region in regions:
+            region_avg = avg_price_by_region.get(region, 0)
+            result[f"price_diff_{region}"] = result["real_time_price"] - region_avg
+
+    return result
+
+
+__all__ = ["add_regional_features"]