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/api-fetch/build/middlewares/http-v1.js

@@ -0,0 +1,50 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.default = void 0;
+/**
+ * Set of HTTP methods which are eligible to be overridden.
+ *
+ * @type {Set<string>}
+ */
+const OVERRIDE_METHODS = new Set(['PATCH', 'PUT', 'DELETE']);
+
+/**
+ * Default request method.
+ *
+ * "A request has an associated method (a method). Unless stated otherwise it
+ * is `GET`."
+ *
+ * @see  https://fetch.spec.whatwg.org/#requests
+ *
+ * @type {string}
+ */
+const DEFAULT_METHOD = 'GET';
+
+/**
+ * API Fetch middleware which overrides the request method for HTTP v1
+ * compatibility leveraging the REST API X-HTTP-Method-Override header.
+ *
+ * @type {import('../types').APIFetchMiddleware}
+ */
+const httpV1Middleware = (options, next) => {
+  const {
+    method = DEFAULT_METHOD
+  } = options;
+  if (OVERRIDE_METHODS.has(method.toUpperCase())) {
+    options = {
+      ...options,
+      headers: {
+        ...options.headers,
+        'X-HTTP-Method-Override': method,
+        'Content-Type': 'application/json'
+      },
+      method: 'POST'
+    };
+  }
+  return next(options);
+};
+var _default = exports.default = httpV1Middleware;
+//# sourceMappingURL=http-v1.js.map