fix: default dashboard to hidden on load

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: DavidLiedle

web/index.html

@@ -1072,7 +1072,7 @@
 // =========================================================================
 const dashDiv = document.getElementById('dashboard');
 const dashBtn = document.getElementById('dash-btn');
-let dashVisible = window.innerWidth > 768;
+let dashVisible = false;
 
 function toggleDashboard() {
   dashVisible = !dashVisible;