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/functions.js

@@ -0,0 +1,31 @@
+var baseFunctions = require('./_baseFunctions'),
+    keys = require('./keys');
+
+/**
+ * Creates an array of function property names from own enumerable properties
+ * of `object`.
+ *
+ * @static
+ * @since 0.1.0
+ * @memberOf _
+ * @category Object
+ * @param {Object} object The object to inspect.
+ * @returns {Array} Returns the function names.
+ * @see _.functionsIn
+ * @example
+ *
+ * function Foo() {
+ *   this.a = _.constant('a');
+ *   this.b = _.constant('b');
+ * }
+ *
+ * Foo.prototype.c = _.constant('c');
+ *
+ * _.functions(new Foo);
+ * // => ['a', 'b']
+ */
+function functions(object) {
+  return object == null ? [] : baseFunctions(object, keys(object));
+}
+
+module.exports = functions;