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/stylelint/lib/utils/isSharedLineComment.js

@@ -0,0 +1,56 @@
+'use strict';
+
+const getNextNonSharedLineCommentNode = require('./getNextNonSharedLineCommentNode');
+const getPreviousNonSharedLineCommentNode = require('./getPreviousNonSharedLineCommentNode');
+const { isRoot, isComment } = require('./typeGuards');
+
+/** @typedef {import('postcss').Node} PostcssNode */
+
+/**
+ *
+ * @param {PostcssNode | void} a
+ * @param {PostcssNode | void} b
+ */
+function nodesShareLines(a, b) {
+	const aLine = a && a.source && a.source.end && a.source.end.line;
+	const bLine = b && b.source && b.source.start && b.source.start.line;
+
+	return aLine === bLine;
+}
+
+/**
+ * @param {PostcssNode} node
+ * @returns {boolean}
+ */
+module.exports = function isSharedLineComment(node) {
+	if (!isComment(node)) {
+		return false;
+	}
+
+	const previousNonSharedLineCommentNode = getPreviousNonSharedLineCommentNode(node);
+
+	if (nodesShareLines(previousNonSharedLineCommentNode, node)) {
+		return true;
+	}
+
+	const nextNonSharedLineCommentNode = getNextNonSharedLineCommentNode(node);
+
+	if (nextNonSharedLineCommentNode && nodesShareLines(node, nextNonSharedLineCommentNode)) {
+		return true;
+	}
+
+	const parentNode = node.parent;
+
+	// It's a first child and located on the same line as block start
+	if (
+		parentNode !== undefined &&
+		!isRoot(parentNode) &&
+		parentNode.index(node) === 0 &&
+		node.raws.before !== undefined &&
+		!node.raws.before.includes('\n')
+	) {
+		return true;
+	}
+
+	return false;
+};