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/toFinite.js

@@ -0,0 +1,42 @@
+var toNumber = require('./toNumber');
+
+/** Used as references for various `Number` constants. */
+var INFINITY = 1 / 0,
+    MAX_INTEGER = 1.7976931348623157e+308;
+
+/**
+ * Converts `value` to a finite number.
+ *
+ * @static
+ * @memberOf _
+ * @since 4.12.0
+ * @category Lang
+ * @param {*} value The value to convert.
+ * @returns {number} Returns the converted number.
+ * @example
+ *
+ * _.toFinite(3.2);
+ * // => 3.2
+ *
+ * _.toFinite(Number.MIN_VALUE);
+ * // => 5e-324
+ *
+ * _.toFinite(Infinity);
+ * // => 1.7976931348623157e+308
+ *
+ * _.toFinite('3.2');
+ * // => 3.2
+ */
+function toFinite(value) {
+  if (!value) {
+    return value === 0 ? value : 0;
+  }
+  value = toNumber(value);
+  if (value === INFINITY || value === -INFINITY) {
+    var sign = (value < 0 ? -1 : 1);
+    return sign * MAX_INTEGER;
+  }
+  return value === value ? value : 0;
+}
+
+module.exports = toFinite;