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/services/__init__.py

@@ -0,0 +1,13 @@
+from app.services.data_service import DataService
+from app.services.strategy_service import StrategyService
+from app.services.ml_service import MLService
+from app.services.trading_service import TradingService
+from app.services.alert_service import AlertService
+
+__all__ = [
+    "DataService",
+    "StrategyService",
+    "MLService",
+    "TradingService",
+    "AlertService",
+]