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/comment-parser/tests/unit/transforms.spec.ts

@@ -0,0 +1,21 @@
+import { flow } from '../../src/transforms/index.js';
+import { seedBlock } from '../../src/util.js';
+import { Block } from '../../src/primitives.js';
+
+const t0 = (b: Block): Block => ({ ...b, description: b.description + ' t0' });
+const t1 = (b: Block): Block => ({ ...b, description: b.description + ' t1' });
+
+test('multiple', () => {
+  const block = seedBlock({ description: 'test' });
+  expect(flow(t0, t1)(block).description).toBe('test t0 t1');
+});
+
+test('one', () => {
+  const block = seedBlock({ description: 'test' });
+  expect(flow(t0)(block).description).toBe('test t0');
+});
+
+test('none', () => {
+  const block = seedBlock({ description: 'test' });
+  expect(flow()(block).description).toBe('test');
+});