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/api/websocket.py

@@ -0,0 +1,57 @@
+"""
+WebSocket endpoint pour le streaming de données live.
+
+Broadcast les événements du bot (ticks, nouveaux trades, etc.)
+vers tous les clients connectés.
+"""
+
+import asyncio
+import json
+import logging
+from typing import Set
+
+from fastapi import WebSocket, WebSocketDisconnect
+
+logger = logging.getLogger(__name__)
+
+
+class ConnectionManager:
+    def __init__(self) -> None:
+        self._active: Set[WebSocket] = set()
+
+    async def connect(self, ws: WebSocket) -> None:
+        await ws.accept()
+        self._active.add(ws)
+        logger.info("WS client connecté — %d total", len(self._active))
+
+    def disconnect(self, ws: WebSocket) -> None:
+        self._active.discard(ws)
+        logger.info("WS client déconnecté — %d restants", len(self._active))
+
+    async def broadcast(self, data: dict) -> None:
+        if not self._active:
+            return
+        message = json.dumps(data, default=str)
+        dead: Set[WebSocket] = set()
+        for ws in list(self._active):
+            try:
+                await ws.send_text(message)
+            except Exception:
+                dead.add(ws)
+        for ws in dead:
+            self.disconnect(ws)
+
+
+manager = ConnectionManager()
+
+
+async def websocket_endpoint(ws: WebSocket) -> None:
+    await manager.connect(ws)
+    try:
+        while True:
+            # Garder la connexion ouverte, le client peut envoyer des pings
+            data = await ws.receive_text()
+            if data == "ping":
+                await ws.send_text(json.dumps({"type": "pong"}))
+    except WebSocketDisconnect:
+        manager.disconnect(ws)