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/third-party-web/lib/create-entity-finder-api.test.js

@@ -0,0 +1,44 @@
+const {createAPIFromDataset} = require('./create-entity-finder-api.js')
+
+describe('getEntity', () => {
+  let api
+
+  beforeEach(() => {
+    api = createAPIFromDataset([
+      {
+        name: 'Domain',
+        domains: ['*.example.com', '*.example.co.uk'],
+      },
+      {
+        name: 'Subdomain',
+        domains: ['*.sub.example.com', '*.sub.example.co.uk'],
+      },
+      {
+        name: 'Subsubdomain',
+        domains: ['very.specific.example.com'],
+      },
+    ])
+  })
+
+  it('should find direct domains', () => {
+    expect(api.getEntity('https://very.specific.example.com/path').name).toEqual('Subsubdomain')
+  })
+
+  it('should find wildcard subdomains', () => {
+    expect(api.getEntity('https://foo.sub.example.com/path').name).toEqual('Subdomain')
+    expect(api.getEntity('https://bar.sub.example.com/path').name).toEqual('Subdomain')
+    expect(api.getEntity('https://baz.bar.sub.example.com/path').name).toEqual('Subdomain')
+    expect(api.getEntity('https://foo.sub.example.co.uk/path').name).toEqual('Subdomain')
+    expect(api.getEntity('https://bar.sub.example.co.uk/path').name).toEqual('Subdomain')
+    expect(api.getEntity('https://baz.bar.sub.example.co.uk/path').name).toEqual('Subdomain')
+  })
+
+  it('should find wildcard domains', () => {
+    expect(api.getEntity('https://foo.example.com/path').name).toEqual('Domain')
+    expect(api.getEntity('https://bar.example.com/path').name).toEqual('Domain')
+    expect(api.getEntity('https://baz.bar.example.com/path').name).toEqual('Domain')
+    expect(api.getEntity('https://foo.example.co.uk/path').name).toEqual('Domain')
+    expect(api.getEntity('https://bar.example.co.uk/path').name).toEqual('Domain')
+    expect(api.getEntity('https://baz.bar.example.co.uk/path').name).toEqual('Domain')
+  })
+})