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/engine/strategies/base.py

@@ -5,7 +5,7 @@ from collections.abc import Sequence
 from dataclasses import dataclass
 from typing import Any, ClassVar, Literal, Protocol
 
-from app.engine.indicators import atr, ema, rolling_std, rsi, sma
+from app.engine.indicators import atr, ema, macd, roc, rolling_std, rsi, sma
 from app.models import PositionSide
 from app.schemas import Candle, ParamSpec, StrategyOut
 
@@ -106,6 +106,15 @@ class StrategyContext:
     def std(self, period: int = 20) -> float | None:
         return rolling_std(self.closes, period)[-1]
 
+    def macd(
+        self, fast: int = 12, slow: int = 26, signal: int = 9
+    ) -> tuple[float | None, float | None, float | None]:
+        macd_line, signal_line, histogram = macd(self.closes, fast, slow, signal)
+        return macd_line[-1], signal_line[-1], histogram[-1]
+
+    def roc(self, period: int = 10) -> float | None:
+        return roc(self.closes, period)[-1]
+
     # --- order intents ------------------------------------------------
     def enter_long(
         self,