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/sides-bottom.js

@@ -0,0 +1,21 @@
+import { createElement } from "react";
+/**
+ * WordPress dependencies
+ */
+import { SVG, Path } from '@wordpress/primitives';
+const sidesBottom = createElement(SVG, {
+  xmlns: "http://www.w3.org/2000/svg",
+  viewBox: "0 0 24 24"
+}, createElement(Path, {
+  d: "m7.5 6h9v-1.5h-9zm0 13.5h9v-1.5h-9zm-3-3h1.5v-9h-1.5zm13.5-9v9h1.5v-9z",
+  style: {
+    opacity: 0.25
+  }
+}), createElement(Path, {
+  d: "m16.5 19.5h-9v-1.5h9z",
+  style: {
+    fill: '#1e1e1e'
+  }
+}));
+export default sidesBottom;
+//# sourceMappingURL=sides-bottom.js.map