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/mimic-fn/readme.md

@@ -0,0 +1,69 @@
+# mimic-fn [![Build Status](https://travis-ci.org/sindresorhus/mimic-fn.svg?branch=master)](https://travis-ci.org/sindresorhus/mimic-fn)
+
+> Make a function mimic another one
+
+Useful when you wrap a function in another function and like to preserve the original name and other properties.
+
+
+## Install
+
+```
+$ npm install mimic-fn
+```
+
+
+## Usage
+
+```js
+const mimicFn = require('mimic-fn');
+
+function foo() {}
+foo.unicorn = '🦄';
+
+function wrapper() {
+	return foo();
+}
+
+console.log(wrapper.name);
+//=> 'wrapper'
+
+mimicFn(wrapper, foo);
+
+console.log(wrapper.name);
+//=> 'foo'
+
+console.log(wrapper.unicorn);
+//=> '🦄'
+```
+
+
+## API
+
+It will copy over the properties `name`, `length`, `displayName`, and any custom properties you may have set.
+
+### mimicFn(to, from)
+
+Modifies the `to` function and returns it.
+
+#### to
+
+Type: `Function`
+
+Mimicking function.
+
+#### from
+
+Type: `Function`
+
+Function to mimic.
+
+
+## Related
+
+- [rename-fn](https://github.com/sindresorhus/rename-fn) - Rename a function
+- [keep-func-props](https://github.com/ehmicky/keep-func-props) - Wrap a function without changing its name, length and other properties
+
+
+## License
+
+MIT © [Sindre Sorhus](https://sindresorhus.com)