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-jsx-a11y/docs/rules/no-access-key.md

@@ -0,0 +1,30 @@
+# jsx-a11y/no-access-key
+
+💼 This rule is enabled in the following configs: ☑️ `recommended`, 🔒 `strict`.
+
+<!-- end auto-generated rule header -->
+
+Enforce no accessKey prop on element. Access keys are HTML attributes that allow web developers to assign keyboard shortcuts to elements. Inconsistencies between keyboard shortcuts and keyboard commands used by screen readers and keyboard-only users create accessibility complications so to avoid complications, access keys should not be used.
+
+### References
+1. [WebAIM](https://webaim.org/techniques/keyboard/accesskey#spec)
+
+## Rule details
+
+This rule takes no arguments.
+
+### Succeed
+```jsx
+<div />
+```
+
+### Fail
+```jsx
+<div accessKey="h" />
+```
+
+## Accessibility guidelines
+General best practice (reference resources)
+
+### Resources
+- [WebAIM, Keyboard Accessibility: Accesskey](https://webaim.org/techniques/keyboard/accesskey#spec)