Implement FastAPI backend and Vue 3 frontend for Lowkey Backtest UI

- Added FastAPI backend with core API endpoints for strategies, backtests, and data management.
- Introduced Vue 3 frontend with a dark theme, enabling users to run backtests, adjust parameters, and compare results.
- Implemented Pydantic schemas for request/response validation and SQLAlchemy models for database interactions.
- Enhanced project structure with dedicated modules for services, routers, and components.
- Updated dependencies in `pyproject.toml` and `frontend/package.json` to include FastAPI, SQLAlchemy, and Vue-related packages.
- Improved `.gitignore` to exclude unnecessary files and directories.

api/models/database.py

@@ -0,0 +1,99 @@
+"""
+SQLAlchemy database models and session management for backtest run persistence.
+"""
+import json
+from datetime import datetime, timezone
+from pathlib import Path
+
+from sqlalchemy import JSON, Column, DateTime, Float, Integer, String, Text, create_engine
+from sqlalchemy.orm import DeclarativeBase, Session, sessionmaker
+
+# Database file location
+DB_PATH = Path(__file__).parent.parent.parent / "data" / "backtest_runs.db"
+DATABASE_URL = f"sqlite:///{DB_PATH}"
+
+engine = create_engine(DATABASE_URL, connect_args={"check_same_thread": False})
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+
+class Base(DeclarativeBase):
+    """Base class for SQLAlchemy models."""
+    pass
+
+
+class BacktestRun(Base):
+    """
+    Persisted backtest run record.
+    
+    Stores all information needed to display and compare runs.
+    """
+    __tablename__ = "backtest_runs"
+    
+    id = Column(Integer, primary_key=True, autoincrement=True)
+    run_id = Column(String(36), unique=True, nullable=False, index=True)
+    
+    # Configuration
+    strategy = Column(String(50), nullable=False, index=True)
+    symbol = Column(String(20), nullable=False, index=True)
+    exchange = Column(String(20), nullable=False, default="okx")
+    market_type = Column(String(20), nullable=False)
+    timeframe = Column(String(10), nullable=False)
+    leverage = Column(Integer, nullable=False, default=1)
+    params = Column(JSON, nullable=False, default=dict)
+    
+    # Date range
+    start_date = Column(String(20), nullable=True)
+    end_date = Column(String(20), nullable=True)
+    
+    # Metrics (denormalized for quick listing)
+    total_return = Column(Float, nullable=False)
+    benchmark_return = Column(Float, nullable=False, default=0.0)
+    alpha = Column(Float, nullable=False, default=0.0)
+    sharpe_ratio = Column(Float, nullable=False)
+    max_drawdown = Column(Float, nullable=False)
+    win_rate = Column(Float, nullable=False)
+    total_trades = Column(Integer, nullable=False)
+    profit_factor = Column(Float, nullable=True)
+    total_fees = Column(Float, nullable=False, default=0.0)
+    total_funding = Column(Float, nullable=False, default=0.0)
+    liquidation_count = Column(Integer, nullable=False, default=0)
+    liquidation_loss = Column(Float, nullable=False, default=0.0)
+    adjusted_return = Column(Float, nullable=True)
+    
+    # Full data (JSON serialized)
+    equity_curve = Column(Text, nullable=False)  # JSON array
+    trades = Column(Text, nullable=False)  # JSON array
+    
+    # Metadata
+    created_at = Column(DateTime, nullable=False, default=lambda: datetime.now(timezone.utc))
+    
+    def set_equity_curve(self, data: list[dict]):
+        """Serialize equity curve to JSON string."""
+        self.equity_curve = json.dumps(data)
+    
+    def get_equity_curve(self) -> list[dict]:
+        """Deserialize equity curve from JSON string."""
+        return json.loads(self.equity_curve) if self.equity_curve else []
+    
+    def set_trades(self, data: list[dict]):
+        """Serialize trades to JSON string."""
+        self.trades = json.dumps(data)
+    
+    def get_trades(self) -> list[dict]:
+        """Deserialize trades from JSON string."""
+        return json.loads(self.trades) if self.trades else []
+
+
+def init_db():
+    """Create database tables if they don't exist."""
+    DB_PATH.parent.mkdir(parents=True, exist_ok=True)
+    Base.metadata.create_all(bind=engine)
+
+
+def get_db() -> Session:
+    """Get database session (dependency injection)."""
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()