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/eslint-plugin-jest/docs/rules/no-restricted-jest-methods.md

@@ -0,0 +1,51 @@
+# Disallow specific `jest.` methods (`no-restricted-jest-methods`)
+
+<!-- end auto-generated rule header -->
+
+You may wish to restrict the use of specific `jest` methods.
+
+## Rule details
+
+This rule checks for the usage of specific methods on the `jest` object, which
+can be used to disallow certain patterns such as spies and mocks.
+
+## Options
+
+Restrictions are expressed in the form of a map, with the value being either a
+string message to be shown, or `null` if a generic default message should be
+used.
+
+By default, this map is empty, meaning no `jest` methods are banned.
+
+For example:
+
+```json
+{
+  "jest/no-restricted-jest-methods": [
+    "error",
+    {
+      "advanceTimersByTime": null,
+      "spyOn": "Don't use spies"
+    }
+  ]
+}
+```
+
+Examples of **incorrect** code for this rule with the above configuration
+
+```js
+jest.useFakeTimers();
+it('calls the callback after 1 second via advanceTimersByTime', () => {
+  // ...
+
+  jest.advanceTimersByTime(1000);
+
+  // ...
+});
+
+test('plays video', () => {
+  const spy = jest.spyOn(video, 'play');
+
+  // ...
+});
+```