Remove icons from page title bars and fix Features page issues

- Remove icons from all page title sections in tab bars
- Fix double padding on mobile for Features page
- Fix drag state not resetting when Apply/Cancel pressed

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

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

frontend/src/styles/Layout.css

@@ -272,6 +272,12 @@ body {
   width: 100%;
 }
 
+/* Remove double padding when theme-tab-content is nested inside admin-tab-content */
+.admin-tab-content .theme-tab-content {
+  padding: 0;
+  max-width: none;
+}
+
 /* ==========  RESPONSIVE DESIGN ========== */
 
 /* Tablet - reduce padding */