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/models/__init__.py

@@ -0,0 +1,52 @@
+from app.models.schemas import (
+    PriceData,
+    BatteryState,
+    BacktestConfig,
+    BacktestMetrics,
+    TrainingRequest,
+    PredictionResponse,
+    ModelInfo,
+    TrainingStatus,
+    ArbitrageOpportunity,
+    DashboardSummary,
+    Trade,
+    StrategyStatus,
+    Alert,
+    AppSettings,
+)
+
+from app.models.enums import (
+    RegionEnum,
+    FuelTypeEnum,
+    StrategyEnum,
+    TradeTypeEnum,
+    BacktestStatusEnum,
+    ModelType,
+    AlertTypeEnum,
+    TrainingStatusEnum,
+)
+
+__all__ = [
+    "PriceData",
+    "BatteryState",
+    "BacktestConfig",
+    "BacktestMetrics",
+    "TrainingRequest",
+    "PredictionResponse",
+    "ModelInfo",
+    "TrainingStatus",
+    "ArbitrageOpportunity",
+    "DashboardSummary",
+    "Trade",
+    "StrategyStatus",
+    "Alert",
+    "AppSettings",
+    "RegionEnum",
+    "FuelTypeEnum",
+    "StrategyEnum",
+    "TradeTypeEnum",
+    "BacktestStatusEnum",
+    "ModelType",
+    "AlertTypeEnum",
+    "TrainingStatusEnum",
+]