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/postcss-selector-parser/dist/util/stripComments.js

@@ -0,0 +1,21 @@
+"use strict";
+
+exports.__esModule = true;
+exports["default"] = stripComments;
+function stripComments(str) {
+  var s = "";
+  var commentStart = str.indexOf("/*");
+  var lastEnd = 0;
+  while (commentStart >= 0) {
+    s = s + str.slice(lastEnd, commentStart);
+    var commentEnd = str.indexOf("*/", commentStart + 2);
+    if (commentEnd < 0) {
+      return s;
+    }
+    lastEnd = commentEnd + 2;
+    commentStart = str.indexOf("/*", lastEnd);
+  }
+  s = s + str.slice(lastEnd);
+  return s;
+}
+module.exports = exports.default;