Move ASCII banner into boot sequence, fix remaining UI issues

- Remove collapsible ASCII banner from dashboard (was cluttering the UI)
- Show ASCII banner in the boot overlay on first session visit, above
  the boot messages, with a 400ms pause before messages begin
- Add scroll fade indicator (green-tinted gradient edges) to .table-wrapper
  so users can see when the table is horizontally scrollable
- Fix null guards for tab switcher in ticket.js (tabEl, activeBtn)
- Fix Reset → RESET uppercase in AuditLogView and UserActivityView

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

assets/js/ticket.js

@@ -548,10 +548,13 @@ function showTab(tabName) {
     });
 
     // Show selected tab and activate its button
-    document.getElementById(`${tabName}-tab`).style.display = 'block';
+    const tabEl = document.getElementById(`${tabName}-tab`);
+    if (tabEl) tabEl.style.display = 'block';
     const activeBtn = document.querySelector(`.tab-btn[data-tab="${tabName}"]`);
-    activeBtn.classList.add('active');
-    activeBtn.setAttribute('aria-selected', 'true');
+    if (activeBtn) {
+        activeBtn.classList.add('active');
+        activeBtn.setAttribute('aria-selected', 'true');
+    }
 
     // Load attachments when tab is shown
     if (tabName === 'attachments') {