feat: trading bot MVP — ICT Order Block + Liquidity Sweep strategy

Full-stack trading bot with:
- FastAPI backend with ICT strategy (Order Block + Liquidity Sweep detection)
- Backtester engine with rolling window, spread simulation, and performance metrics
- Hybrid market data service (yfinance + TwelveData with rate limiting + SQLite cache)
- Simulated exchange for paper trading
- React/TypeScript frontend with TradingView lightweight-charts v5
- Live dashboard with candlestick chart, OHLC legend, trade markers
- Backtest page with configurable parameters, equity curve, and trade table
- WebSocket support for real-time updates
- Bot runner with asyncio loop for automated trading

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/models/candle.py

@@ -0,0 +1,25 @@
+from datetime import datetime
+
+from sqlalchemy import Float, Integer, String, DateTime, UniqueConstraint
+from sqlalchemy.orm import Mapped, mapped_column
+
+from app.core.database import Base
+
+
+class Candle(Base):
+    __tablename__ = "candles"
+    __table_args__ = (
+        # Garantit INSERT OR IGNORE sur (instrument, granularity, time)
+        UniqueConstraint("instrument", "granularity", "time", name="uq_candle"),
+    )
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True)
+    instrument: Mapped[str] = mapped_column(String(20), index=True)
+    granularity: Mapped[str] = mapped_column(String(10))
+    time: Mapped[datetime] = mapped_column(DateTime, index=True)
+    open: Mapped[float] = mapped_column(Float)
+    high: Mapped[float] = mapped_column(Float)
+    low: Mapped[float] = mapped_column(Float)
+    close: Mapped[float] = mapped_column(Float)
+    volume: Mapped[int] = mapped_column(Integer, default=0)
+    complete: Mapped[bool] = mapped_column(default=True)