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/date-fns/esm/_lib/setUTCISOWeek/index.js

@@ -0,0 +1,12 @@
+import toInteger from "../toInteger/index.js";
+import toDate from "../../toDate/index.js";
+import getUTCISOWeek from "../getUTCISOWeek/index.js";
+import requiredArgs from "../requiredArgs/index.js";
+export default function setUTCISOWeek(dirtyDate, dirtyISOWeek) {
+  requiredArgs(2, arguments);
+  var date = toDate(dirtyDate);
+  var isoWeek = toInteger(dirtyISOWeek);
+  var diff = getUTCISOWeek(date) - isoWeek;
+  date.setUTCDate(date.getUTCDate() - diff * 7);
+  return date;
+}