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/dash.js

@@ -0,0 +1,43 @@
+'use strict';
+
+var parse = require('../');
+var test = require('tape');
+
+test('-', function (t) {
+	t.plan(6);
+	t.deepEqual(parse(['-n', '-']), { n: '-', _: [] });
+	t.deepEqual(parse(['--nnn', '-']), { nnn: '-', _: [] });
+	t.deepEqual(parse(['-']), { _: ['-'] });
+	t.deepEqual(parse(['-f-']), { f: '-', _: [] });
+	t.deepEqual(
+		parse(['-b', '-'], { boolean: 'b' }),
+		{ b: true, _: ['-'] }
+	);
+	t.deepEqual(
+		parse(['-s', '-'], { string: 's' }),
+		{ s: '-', _: [] }
+	);
+});
+
+test('-a -- b', function (t) {
+	t.plan(2);
+	t.deepEqual(parse(['-a', '--', 'b']), { a: true, _: ['b'] });
+	t.deepEqual(parse(['--a', '--', 'b']), { a: true, _: ['b'] });
+});
+
+test('move arguments after the -- into their own `--` array', function (t) {
+	t.plan(1);
+	t.deepEqual(
+		parse(['--name', 'John', 'before', '--', 'after'], { '--': true }),
+		{ name: 'John', _: ['before'], '--': ['after'] }
+	);
+});
+
+test('--- option value', function (t) {
+	// A multi-dash value is largely an edge case, but check the behaviour is as expected,
+	// and in particular the same for short option and long option (as made consistent in Jan 2023).
+	t.plan(2);
+	t.deepEqual(parse(['-n', '---']), { n: '---', _: [] });
+	t.deepEqual(parse(['--nnn', '---']), { nnn: '---', _: [] });
+});
+