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/_hashGet.js

@@ -0,0 +1,30 @@
+var nativeCreate = require('./_nativeCreate');
+
+/** Used to stand-in for `undefined` hash values. */
+var HASH_UNDEFINED = '__lodash_hash_undefined__';
+
+/** Used for built-in method references. */
+var objectProto = Object.prototype;
+
+/** Used to check objects for own properties. */
+var hasOwnProperty = objectProto.hasOwnProperty;
+
+/**
+ * Gets the hash value for `key`.
+ *
+ * @private
+ * @name get
+ * @memberOf Hash
+ * @param {string} key The key of the value to get.
+ * @returns {*} Returns the entry value.
+ */
+function hashGet(key) {
+  var data = this.__data__;
+  if (nativeCreate) {
+    var result = data[key];
+    return result === HASH_UNDEFINED ? undefined : result;
+  }
+  return hasOwnProperty.call(data, key) ? data[key] : undefined;
+}
+
+module.exports = hashGet;