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>

rcon.css

@@ -3,7 +3,7 @@
 :root {
   --rcon-bg: #252830;
   --rcon-text: #cfd2da;
-  --rcon-accent: #a78bfa;
+  --rcon-accent: #8b5cf6;
   --rcon-card-bg: #434857;
   /* Override BS5 dark theme body background */
   --bs-body-bg: #252830;
@@ -41,7 +41,7 @@ a:hover { color: #fff; text-decoration: none; }
 .nav-sidebar .nav-link:hover,
 .nav-sidebar .nav-link.active {
   color: #fff;
-  background-color: #8b5cf6;
+  background-color: #6d28d9;
 }
 
 /* Fade utility */
@@ -78,7 +78,7 @@ a:hover { color: #fff; text-decoration: none; }
   background: rgba(255, 255, 255, 0.2);
   color: #fff;
   border-color: var(--rcon-accent);
-  box-shadow: 0 0 0 0.2rem rgba(139, 92, 246, 0.25);
+  box-shadow: 0 0 0 0.2rem rgba(109, 40, 217, 0.25);
 }
 
 /* Cards — override BS dark-theme bg to our darker shade */
@@ -111,13 +111,6 @@ a:hover { color: #fff; text-decoration: none; }
   color: rgba(255, 255, 255, 0.85);
 }
 
-/* Page title */
-#page-title {
-  padding-bottom: 0.5rem;
-  margin-bottom: 1rem;
-  border-bottom: 1px solid rgba(255, 255, 255, 0.15);
-}
-
 /* Chart SVGs */
 #chart-performance,
 #chart-network,