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/enums.py

@@ -0,0 +1,60 @@
+from enum import Enum
+
+
+class RegionEnum(str, Enum):
+    FR = "FR"
+    BE = "BE"
+    DE = "DE"
+    NL = "NL"
+    UK = "UK"
+
+
+class FuelTypeEnum(str, Enum):
+    GAS = "gas"
+    NUCLEAR = "nuclear"
+    COAL = "coal"
+    SOLAR = "solar"
+    WIND = "wind"
+    HYDRO = "hydro"
+
+
+class StrategyEnum(str, Enum):
+    FUNDAMENTAL = "fundamental"
+    TECHNICAL = "technical"
+    ML = "ml"
+    MINING = "mining"
+
+
+class TradeTypeEnum(str, Enum):
+    BUY = "buy"
+    SELL = "sell"
+    CHARGE = "charge"
+    DISCHARGE = "discharge"
+
+
+class BacktestStatusEnum(str, Enum):
+    PENDING = "pending"
+    RUNNING = "running"
+    COMPLETED = "completed"
+    FAILED = "failed"
+    CANCELLED = "cancelled"
+
+
+class ModelType(str, Enum):
+    PRICE_PREDICTION = "price_prediction"
+    RL_BATTERY = "rl_battery"
+
+
+class AlertTypeEnum(str, Enum):
+    PRICE_SPIKE = "price_spike"
+    ARBITRAGE_OPPORTUNITY = "arbitrage_opportunity"
+    BATTERY_LOW = "battery_low"
+    BATTERY_FULL = "battery_full"
+    STRATEGY_ERROR = "strategy_error"
+
+
+class TrainingStatusEnum(str, Enum):
+    PENDING = "pending"
+    RUNNING = "running"
+    COMPLETED = "completed"
+    FAILED = "failed"