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/__init__.py

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+from app.utils.logger import get_logger
+
+logger = get_logger(__name__)
+
+__all__ = ["logger"]

backend/app/utils/helpers.py

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+from datetime import datetime, timedelta
+from typing import Optional
+import pytz
+
+
+def utcnow() -> datetime:
+    """Get current UTC datetime."""
+    return datetime.now(pytz.UTC)
+
+
+def parse_date(date_str: str) -> datetime:
+    """Parse date string to datetime."""
+    formats = ["%Y-%m-%d", "%Y-%m-%dT%H:%M:%S", "%Y-%m-%d %H:%M:%S"]
+    for fmt in formats:
+        try:
+            return datetime.strptime(date_str, fmt)
+        except ValueError:
+            continue
+    raise ValueError(f"Unable to parse date: {date_str}")
+
+
+def format_timestamp(dt: datetime, format_str: str = "%Y-%m-%dT%H:%M:%S") -> str:
+    """Format datetime to string."""
+    return dt.strftime(format_str)
+
+
+def calculate_time_delta(start: datetime, end: datetime) -> timedelta:
+    """Calculate time delta between two datetimes."""
+    return end - start
+
+
+def safe_divide(a: float, b: float, default: float = 0.0) -> float:
+    """Safely divide two numbers with default fallback."""
+    if b == 0:
+        return default
+    return a / b

backend/app/utils/logger.py

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+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",
+    )