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/helpers.py

@@ -0,0 +1,36 @@
+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