Fix dark mode bulk toolbar, light mode timeline, and activity tab visibility

- Changed bulk-actions-toolbar dark mode background from #1a1a00 to #2d3748
- Fixed timeline-content light mode background from #1a202c to #f8f9fa
- Added activity-tab to showTab() function to properly hide/show all tabs

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

assets/js/ticket.js

@@ -363,21 +363,25 @@ function showTab(tabName) {
     // Hide all tab contents
     const descriptionTab = document.getElementById('description-tab');
     const commentsTab = document.getElementById('comments-tab');
-    
+    const activityTab = document.getElementById('activity-tab');
+
     if (!descriptionTab || !commentsTab) {
         console.error('Tab elements not found');
         return;
     }
-    
-    // Hide both tabs
+
+    // Hide all tabs
     descriptionTab.style.display = 'none';
     commentsTab.style.display = 'none';
-    
+    if (activityTab) {
+        activityTab.style.display = 'none';
+    }
+
     // Remove active class from all buttons
     document.querySelectorAll('.tab-btn').forEach(btn => {
         btn.classList.remove('active');
     });
-    
+
     // Show selected tab and activate its button
     document.getElementById(`${tabName}-tab`).style.display = 'block';
     document.querySelector(`[onclick="showTab('${tabName}')"]`).classList.add('active');