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/stylelintCommand.js

@@ -0,0 +1,53 @@
+'use strict';
+
+const { assertString } = require('./validateTypes');
+
+const DISABLE_COMMAND = 'stylelint-disable';
+const DISABLE_LINE_COMMAND = 'stylelint-disable-line';
+const DISABLE_NEXT_LINE_COMMAND = 'stylelint-disable-next-line';
+const ENABLE_COMMAND = 'stylelint-enable';
+
+const ALL_COMMANDS = new Set([
+	DISABLE_COMMAND,
+	DISABLE_LINE_COMMAND,
+	DISABLE_NEXT_LINE_COMMAND,
+	ENABLE_COMMAND,
+]);
+
+/** @typedef {import('postcss').Comment} Comment */
+
+/**
+ * Extract a command from a given comment.
+ *
+ * @param {Comment} comment
+ * @returns {string}
+ */
+function extractStylelintCommand(comment) {
+	const [command] = comment.text.split(/\s/, 1);
+
+	assertString(command);
+
+	return command;
+}
+
+/**
+ * Tests if the given comment is a Stylelint command.
+ *
+ * @param {Comment} comment
+ * @returns {boolean}
+ */
+function isStylelintCommand(comment) {
+	const command = extractStylelintCommand(comment);
+
+	return command !== undefined && ALL_COMMANDS.has(command);
+}
+
+module.exports = {
+	DISABLE_COMMAND,
+	DISABLE_LINE_COMMAND,
+	DISABLE_NEXT_LINE_COMMAND,
+	ENABLE_COMMAND,
+
+	extractStylelintCommand,
+	isStylelintCommand,
+};