style: deeper purple + remove redundant page title

- Darkened primary from #8b5cf6 to #6d28d9 (violet-700) to better
  complement the dark theme
- Removed <h1> page title — the sidebar active highlight already
  tells you which tab you're on
- Cleaned up related CSS and elTitle plumbing in app.js

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

index.html

@@ -11,11 +11,11 @@
     <style>
       /* Mystical purple primary override for Bootstrap 5.3 */
       [data-bs-theme="dark"] {
-        --bs-primary: #8b5cf6;
-        --bs-primary-rgb: 139, 92, 246;
-        --bs-primary-text-emphasis: #b794f4;
-        --bs-primary-bg-subtle: rgba(139, 92, 246, 0.15);
-        --bs-primary-border-subtle: rgba(139, 92, 246, 0.3);
+        --bs-primary: #6d28d9;
+        --bs-primary-rgb: 109, 40, 217;
+        --bs-primary-text-emphasis: #a78bfa;
+        --bs-primary-bg-subtle: rgba(109, 40, 217, 0.15);
+        --bs-primary-border-subtle: rgba(109, 40, 217, 0.3);
       }
     </style>
   </head>
@@ -42,7 +42,6 @@
             <ul class="nav flex-column nav-sidebar" id="sidebar-nav"></ul>
           </div>
           <div class="col-md-10">
-            <h1 id="page-title"></h1>
             <div id="app-view"></div>
           </div>
         </div>