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/default_bool.js

@@ -0,0 +1,37 @@
+'use strict';
+
+var test = require('tape');
+var parse = require('../');
+
+test('boolean default true', function (t) {
+	var argv = parse([], {
+		boolean: 'sometrue',
+		default: { sometrue: true },
+	});
+	t.equal(argv.sometrue, true);
+	t.end();
+});
+
+test('boolean default false', function (t) {
+	var argv = parse([], {
+		boolean: 'somefalse',
+		default: { somefalse: false },
+	});
+	t.equal(argv.somefalse, false);
+	t.end();
+});
+
+test('boolean default to null', function (t) {
+	var argv = parse([], {
+		boolean: 'maybe',
+		default: { maybe: null },
+	});
+	t.equal(argv.maybe, null);
+
+	var argvLong = parse(['--maybe'], {
+		boolean: 'maybe',
+		default: { maybe: null },
+	});
+	t.equal(argvLong.maybe, true);
+	t.end();
+});