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/bare-events/lib/errors.js

@@ -0,0 +1,26 @@
+module.exports = class EventEmitterError extends Error {
+  constructor(msg, code, fn = EventEmitterError, opts) {
+    super(`${code}: ${msg}`, opts)
+    this.code = code
+
+    if (Error.captureStackTrace) {
+      Error.captureStackTrace(this, fn)
+    }
+  }
+
+  get name() {
+    return 'EventEmitterError'
+  }
+
+  static OPERATION_ABORTED(cause, msg = 'Operation aborted') {
+    return new EventEmitterError(msg, 'OPERATION_ABORTED', EventEmitterError.OPERATION_ABORTED, {
+      cause
+    })
+  }
+
+  static UNHANDLED_ERROR(cause, msg = 'Unhandled error') {
+    return new EventEmitterError(msg, 'UNHANDLED_ERROR', EventEmitterError.UNHANDLED_ERROR, {
+      cause
+    })
+  }
+}