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-config-prettier/prettier.js

@@ -0,0 +1,12 @@
+"use strict";
+
+module.exports = {
+  rules: {
+    // These are safe to use as long as the `"prettier/prettier"` rule from
+    // eslint-plugin-prettier isn’t enabled.
+    // These are also included in `"plugin:prettier/recommended"`:
+    // https://github.com/prettier/eslint-plugin-prettier#recommended-configuration
+    "arrow-body-style": 0,
+    "prefer-arrow-callback": 0,
+  },
+};