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).

frontend/public/favicon.svg

@@ -0,0 +1,9 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 32 32" width="32" height="32">
+  <circle cx="16" cy="16" r="16" fill="#F7931A"/>
+  <text x="16" y="23.5" text-anchor="middle" font-family="Arial, Helvetica, sans-serif"
+        font-size="21" font-weight="bold" fill="#ffffff">B</text>
+  <rect x="13.9" y="4.2" width="2.2" height="4.6" rx="1.1" fill="#ffffff"/>
+  <rect x="17.6" y="4.2" width="2.2" height="4.6" rx="1.1" fill="#ffffff"/>
+  <rect x="13.9" y="23.2" width="2.2" height="4.6" rx="1.1" fill="#ffffff"/>
+  <rect x="17.6" y="23.2" width="2.2" height="4.6" rx="1.1" fill="#ffffff"/>
+</svg>