Improve Features page ordering and mobile UI consistency

- Fix mobile Features page to respect lateral borders/padding
- Fix drag state not resetting properly when Apply/Cancel pressed
- Improve mobile UI consistency across all pages

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

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

frontend/src/styles/Layout.css

@@ -162,9 +162,9 @@ body {
 
 .page-tab-btn.active,
 .admin-tab-btn.active {
-  background: linear-gradient(135deg, var(--color-accent) 0%, var(--color-accent-hover) 100%);
+  background: var(--color-accent);
   color: white;
-  box-shadow: 0 2px 8px rgba(var(--color-accent-rgb), 0.3);
+  box-shadow: 0 4px 12px rgba(var(--color-accent-rgb), 0.25);
 }
 
 .page-subtitle {