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/data-urls/lib/utils.js

@@ -0,0 +1,18 @@
+"use strict";
+const { atob } = require("abab");
+
+exports.stripLeadingAndTrailingASCIIWhitespace = string => {
+  return string.replace(/^[ \t\n\f\r]+/u, "").replace(/[ \t\n\f\r]+$/u, "");
+};
+
+exports.isomorphicDecode = input => {
+  return Array.from(input, byte => String.fromCodePoint(byte)).join("");
+};
+
+exports.forgivingBase64Decode = data => {
+  const asString = atob(data);
+  if (asString === null) {
+    return null;
+  }
+  return Uint8Array.from(asString, c => c.codePointAt(0));
+};