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/reakit/es/Portal/Portal.js

@@ -0,0 +1,50 @@
+import { createContext, useContext, useState, createElement } from 'react';
+import { useIsomorphicEffect } from 'reakit-utils/useIsomorphicEffect';
+import { canUseDOM } from 'reakit-utils/canUseDOM';
+import { createPortal } from 'react-dom';
+
+function getBodyElement() {
+  return canUseDOM ? document.body : null;
+}
+
+var PortalContext = /*#__PURE__*/createContext(getBodyElement());
+function Portal(_ref) {
+  var children = _ref.children;
+  // if it's a nested portal, context is the parent portal
+  // otherwise it's document.body
+  // https://github.com/reakit/reakit/issues/513
+  var context = useContext(PortalContext) || getBodyElement();
+
+  var _React$useState = useState(function () {
+    if (canUseDOM) {
+      var element = document.createElement("div");
+      element.className = Portal.__className;
+      return element;
+    } // ssr
+
+
+    return null;
+  }),
+      hostNode = _React$useState[0];
+
+  useIsomorphicEffect(function () {
+    if (!hostNode || !context) return undefined;
+    context.appendChild(hostNode);
+    return function () {
+      context.removeChild(hostNode);
+    };
+  }, [hostNode, context]);
+
+  if (hostNode) {
+    return /*#__PURE__*/createPortal( /*#__PURE__*/createElement(PortalContext.Provider, {
+      value: hostNode
+    }, children), hostNode);
+  } // ssr
+
+
+  return null;
+}
+Portal.__className = "__reakit-portal";
+Portal.__selector = "." + Portal.__className;
+
+export { Portal, PortalContext };

node_modules/reakit/es/Portal/index.js

@@ -0,0 +1,5 @@
+import 'react';
+import 'reakit-utils/useIsomorphicEffect';
+import 'reakit-utils/canUseDOM';
+import 'react-dom';
+export { Portal, PortalContext } from './Portal.js';