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/redux/src/utils/kindOf.js

@@ -0,0 +1,70 @@
+// Inlined / shortened version of `kindOf` from https://github.com/jonschlinkert/kind-of
+function miniKindOf(val) {
+  if (val === void 0) return 'undefined'
+  if (val === null) return 'null'
+
+  const type = typeof val
+  switch (type) {
+    case 'boolean':
+    case 'string':
+    case 'number':
+    case 'symbol':
+    case 'function': {
+      return type
+    }
+    default:
+      break
+  }
+
+  if (Array.isArray(val)) return 'array'
+  if (isDate(val)) return 'date'
+  if (isError(val)) return 'error'
+
+  const constructorName = ctorName(val)
+  switch (constructorName) {
+    case 'Symbol':
+    case 'Promise':
+    case 'WeakMap':
+    case 'WeakSet':
+    case 'Map':
+    case 'Set':
+      return constructorName
+    default:
+      break
+  }
+
+  // other
+  return type.slice(8, -1).toLowerCase().replace(/\s/g, '')
+}
+
+function ctorName(val) {
+  return typeof val.constructor === 'function' ? val.constructor.name : null
+}
+
+function isError(val) {
+  return (
+    val instanceof Error ||
+    (typeof val.message === 'string' &&
+      val.constructor &&
+      typeof val.constructor.stackTraceLimit === 'number')
+  )
+}
+
+function isDate(val) {
+  if (val instanceof Date) return true
+  return (
+    typeof val.toDateString === 'function' &&
+    typeof val.getDate === 'function' &&
+    typeof val.setDate === 'function'
+  )
+}
+
+export function kindOf(val) {
+  let typeOfVal = typeof val
+
+  if (process.env.NODE_ENV !== 'production') {
+    typeOfVal = miniKindOf(val)
+  }
+
+  return typeOfVal
+}