Bitcoin favicon, more strategies, default timeframe 5m

- Add an SVG Bitcoin favicon and link it in index.html.
- New indicators: macd() and roc().
- Five new strategies: macd_trend, bollinger_reversion, donchian_breakout,
  ema_cross, momentum (plus the existing sma_cross, rsi_reversion).
- Default TIMEFRAME is now 5m (config, .env.example, compose, workflow, UI).

backend/app/config.py

@@ -27,7 +27,7 @@ class Settings(BaseSettings):
     mode: str = "paper"
     exchange: str = "binance"
     symbol: str = "BTC/USDT"
-    timeframe: str = "1m"
+    timeframe: str = "5m"
     poll_interval: float = 5.0
     candle_limit: int = 200