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/lodash/_baseAssignValue.js

@@ -0,0 +1,25 @@
+var defineProperty = require('./_defineProperty');
+
+/**
+ * The base implementation of `assignValue` and `assignMergeValue` without
+ * value checks.
+ *
+ * @private
+ * @param {Object} object The object to modify.
+ * @param {string} key The key of the property to assign.
+ * @param {*} value The value to assign.
+ */
+function baseAssignValue(object, key, value) {
+  if (key == '__proto__' && defineProperty) {
+    defineProperty(object, key, {
+      'configurable': true,
+      'enumerable': true,
+      'value': value,
+      'writable': true
+    });
+  } else {
+    object[key] = value;
+  }
+}
+
+module.exports = baseAssignValue;