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/@babel/runtime/helpers/defineProperty.js

@@ -0,0 +1,10 @@
+var toPropertyKey = require("./toPropertyKey.js");
+function _defineProperty(e, r, t) {
+  return (r = toPropertyKey(r)) in e ? Object.defineProperty(e, r, {
+    value: t,
+    enumerable: !0,
+    configurable: !0,
+    writable: !0
+  }) : e[r] = t, e;
+}
+module.exports = _defineProperty, module.exports.__esModule = true, module.exports["default"] = module.exports;