feat: add backtesting functionality with UI and API endpoints

- Introduced backtesting page and fragment in the dashboard for running backtests and viewing recent reports.
- Implemented backtest run logic with configuration options including event path, starting balances, trade capital, and fee profiles.
- Added recent backtest reports storage and retrieval.
- Created a new strategy module for statistical arbitrage experiments with validation on configuration parameters.
- Updated settings to include parameters for the statistical arbitrage strategy.
- Enhanced dashboard controls to support the new strategy mode.
- Added unit tests for backtesting functionality and strategy validation.
- Updated templates for backtesting UI integration.

web/templates/backtesting.html

@@ -0,0 +1,24 @@
+{% extends "base.html" %} {% block title %}{{ title }}{% endblock %} {% block
+content %}
+<section class="hero">
+  <div>
+    <h1 class="title">Backtesting</h1>
+    <p class="subtitle">
+      Replay controls, run status, and recent summary reports.
+    </p>
+  </div>
+  <div class="toolbar">
+    <a class="button secondary" href="{{ dashboard_endpoint }}">Dashboard</a>
+  </div>
+</section>
+
+<section
+  id="backtesting-shell"
+  hx-get="{{ panel_endpoint }}"
+  hx-target="this"
+  hx-trigger="load"
+  hx-swap="outerHTML"
+>
+  {% include "partials/backtesting_panel.html" %}
+</section>
+{% endblock %}