fix: prevent asset conflicts between React and Grid.js versions

Add coexistence checks to all enqueue methods to prevent loading
both React and Grid.js assets simultaneously.

Changes:
- ReactAdmin.php: Only enqueue React assets when ?react=1
- Init.php: Skip Grid.js when React active on admin pages
- Form.php, Coupon.php, Access.php: Restore classic assets when ?react=0
- Customer.php, Product.php, License.php: Add coexistence checks

Now the toggle between Classic and React versions works correctly.

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

node_modules/@wordpress/icons/build-module/library/backup.js

@@ -0,0 +1,13 @@
+import { createElement } from "react";
+/**
+ * WordPress dependencies
+ */
+import { SVG, Path } from '@wordpress/primitives';
+const backup = createElement(SVG, {
+  xmlns: "http://www.w3.org/2000/svg",
+  viewBox: "0 0 24 24"
+}, createElement(Path, {
+  d: "M5.5 12h1.75l-2.5 3-2.5-3H4a8 8 0 113.134 6.35l.907-1.194A6.5 6.5 0 105.5 12zm9.53 1.97l-2.28-2.28V8.5a.75.75 0 00-1.5 0V12a.747.747 0 00.218.529l1.282-.84-1.28.842 2.5 2.5a.75.75 0 101.06-1.061z"
+}));
+export default backup;
+//# sourceMappingURL=backup.js.map