feat: Add database init on startup and documentation

- Add lifespan handler to main.py for automatic DB table creation
- Expand .env.example with detailed variable documentation
- Add AUDIT_REPORT.md with comprehensive product/technical review
- Add STRATEGY_SCHEMA.md as single source of truth for strategy config
- Remove redundant init_db.py script (DB init now handled by app startup)

src/backend/app/main.py

@@ -1,14 +1,35 @@
+import logging
+from contextlib import asynccontextmanager
 from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
 from slowapi import Limiter
 from slowapi.util import get_remote_address
 from .api import auth, bots, backtest, simulate, config, ave
 from .core.limiter import limiter
+from .core.database import engine, Base
+
+logger = logging.getLogger(__name__)
+
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    """Initialize database on startup."""
+    # Import all models to ensure they're registered
+    from .db.models import User, Bot, BotConversation, Backtest, Simulation, Signal
+    
+    # Create tables if they don't exist
+    Base.metadata.create_all(bind=engine)
+    logger.info("Database initialized successfully")
+    
+    yield
+    # Cleanup on shutdown if needed
+
 
 app = FastAPI(
     title="Randebu Trading Bot API",
     description="AI-powered trading bot platform API",
     version="0.1.0",
+    lifespan=lifespan,
 )
 
 app.state.limiter = limiter