Add navigation links between Dashboard and Clearing House

- Dashboard header: green "Clearing House" button linking to /ch/
- Clearing House nav: "← Main Dashboard" link back to /

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

clearing_house/templates/base.html

@@ -203,7 +203,7 @@
       {% if member %}
       <a href="/ch/portfolio" class="{{ 'active' if '/portfolio' in request.path else '' }}">My Portfolio</a>
       {% endif %}
-      <a href="/" target="_blank">Main Dashboard ↗</a>
+      <a href="/">← Main Dashboard</a>
     </div>
     <div class="nav-right">
       {% if member %}

dashboard/templates/index.html

@@ -231,6 +231,7 @@
     <button id="suspend-btn" onclick="toggleSuspend()" class="btn-day btn-suspend" disabled>Suspend</button>
     <button id="mode-btn" onclick="toggleMode()" class="btn-day btn-automatic">Automatic</button>
     {% if frontend_url %}<a href="{{ frontend_url }}" target="_blank" style="margin-left:auto; padding:4px 14px; background:#5c6bc0; color:#fff; border-radius:20px; font-size:12px; font-weight:bold; text-decoration:none;">Frontend</a>{% endif %}
+    <a href="/ch/" target="_blank" style="padding:4px 14px; background:#1a7f37; color:#fff; border-radius:20px; font-size:12px; font-weight:bold; text-decoration:none;">Clearing House</a>
     <a href="/fix/" style="{% if not frontend_url %}margin-left:auto; {% endif %}padding:4px 14px; background:#6c757d; color:#fff; border-radius:20px; font-size:12px; font-weight:bold; text-decoration:none;">FIX UI</a>
   </h1>
   <div class="container">