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/core/config.py

@@ -0,0 +1,22 @@
+from pydantic_settings import BaseSettings, SettingsConfigDict
+
+
+class Settings(BaseSettings):
+    model_config = SettingsConfigDict(env_file=".env", env_file_encoding="utf-8")
+
+    # TwelveData (fallback pour l'intraday historique)
+    # Clé gratuite sur https://twelvedata.com/
+    twelvedata_api_key: str = ""
+
+    # Bot defaults
+    bot_default_instrument: str = "EUR_USD"
+    bot_default_granularity: str = "H1"
+    bot_risk_percent: float = 1.0
+    bot_rr_ratio: float = 2.0
+    bot_initial_balance: float = 10_000.0
+
+    # Database
+    database_url: str = "sqlite+aiosqlite:///./trader_bot.db"
+
+
+settings = Settings()