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/log-symbols/index.js

@@ -0,0 +1,19 @@
+'use strict';
+const chalk = require('chalk');
+const isUnicodeSupported = require('is-unicode-supported');
+
+const main = {
+	info: chalk.blue('ℹ'),
+	success: chalk.green('✔'),
+	warning: chalk.yellow('⚠'),
+	error: chalk.red('✖')
+};
+
+const fallback = {
+	info: chalk.blue('i'),
+	success: chalk.green('√'),
+	warning: chalk.yellow('‼'),
+	error: chalk.red('×')
+};
+
+module.exports = isUnicodeSupported() ? main : fallback;