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/minimist/test/all_bool.js

@@ -0,0 +1,34 @@
+'use strict';
+
+var parse = require('../');
+var test = require('tape');
+
+test('flag boolean true (default all --args to boolean)', function (t) {
+	var argv = parse(['moo', '--honk', 'cow'], {
+		boolean: true,
+	});
+
+	t.deepEqual(argv, {
+		honk: true,
+		_: ['moo', 'cow'],
+	});
+
+	t.deepEqual(typeof argv.honk, 'boolean');
+	t.end();
+});
+
+test('flag boolean true only affects double hyphen arguments without equals signs', function (t) {
+	var argv = parse(['moo', '--honk', 'cow', '-p', '55', '--tacos=good'], {
+		boolean: true,
+	});
+
+	t.deepEqual(argv, {
+		honk: true,
+		tacos: 'good',
+		p: 55,
+		_: ['moo', 'cow'],
+	});
+
+	t.deepEqual(typeof argv.honk, 'boolean');
+	t.end();
+});