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/components/build/toolbar/toolbar-context/index.js

@@ -0,0 +1,20 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.default = void 0;
+var _element = require("@wordpress/element");
+/**
+ * External dependencies
+ */
+// eslint-disable-next-line no-restricted-imports
+
+/**
+ * WordPress dependencies
+ */
+
+const ToolbarContext = (0, _element.createContext)(undefined);
+var _default = ToolbarContext;
+exports.default = _default;
+//# sourceMappingURL=index.js.map

node_modules/@wordpress/components/build/toolbar/toolbar-context/index.js.map

@@ -0,0 +1 @@
+{"version":3,"names":["_element","require","ToolbarContext","createContext","undefined","_default","exports","default"],"sources":["@wordpress/components/src/toolbar/toolbar-context/index.ts"],"sourcesContent":["/**\n * External dependencies\n */\n// eslint-disable-next-line no-restricted-imports\nimport type * as Ariakit from '@ariakit/react';\n\n/**\n * WordPress dependencies\n */\nimport { createContext } from '@wordpress/element';\n\nconst ToolbarContext = createContext< Ariakit.ToolbarStore | undefined >(\n\tundefined\n);\n\nexport default ToolbarContext;\n"],"mappings":";;;;;;AASA,IAAAA,QAAA,GAAAC,OAAA;AATA;AACA;AACA;AACA;;AAGA;AACA;AACA;;AAGA,MAAMC,cAAc,GAAG,IAAAC,sBAAa,EACnCC,SACD,CAAC;AAAC,IAAAC,QAAA,GAEaH,cAAc;AAAAI,OAAA,CAAAC,OAAA,GAAAF,QAAA"}