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/utils/logger.py

@@ -0,0 +1,36 @@
+import os
+from loguru import logger
+import sys
+
+
+def get_logger(name: str):
+    """Get a configured logger instance."""
+    return logger.bind(name=name)
+
+
+def setup_logger():
+    """Setup loguru logger configuration."""
+    logger.remove()
+
+    log_format = (
+        "<green>{time:YYYY-MM-DD HH:mm:ss}</green> | "
+        "<level>{level: <8}</level> | "
+        "<cyan>{name}</cyan>:<cyan>{function}</cyan>:<cyan>{line}</cyan> | "
+        "<level>{message}</level>"
+    )
+
+    logger.add(
+        sys.stdout,
+        format=log_format,
+        level=os.getenv("LOG_LEVEL", "INFO"),
+        colorize=True,
+    )
+
+    logger.add(
+        "logs/app.log",
+        format="{time:YYYY-MM-DD HH:mm:ss} | {level: <8} | {name}:{function}:{line} | {message}",
+        level="DEBUG",
+        rotation="10 MB",
+        retention="7 days",
+        compression="zip",
+    )