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/_getSymbolsIn.js

@@ -0,0 +1,25 @@
+var arrayPush = require('./_arrayPush'),
+    getPrototype = require('./_getPrototype'),
+    getSymbols = require('./_getSymbols'),
+    stubArray = require('./stubArray');
+
+/* Built-in method references for those with the same name as other `lodash` methods. */
+var nativeGetSymbols = Object.getOwnPropertySymbols;
+
+/**
+ * Creates an array of the own and inherited enumerable symbols of `object`.
+ *
+ * @private
+ * @param {Object} object The object to query.
+ * @returns {Array} Returns the array of symbols.
+ */
+var getSymbolsIn = !nativeGetSymbols ? stubArray : function(object) {
+  var result = [];
+  while (object) {
+    arrayPush(result, getSymbols(object));
+    object = getPrototype(object);
+  }
+  return result;
+};
+
+module.exports = getSymbolsIn;