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/ajv/lib/cache.js

@@ -0,0 +1,26 @@
+'use strict';
+
+
+var Cache = module.exports = function Cache() {
+  this._cache = {};
+};
+
+
+Cache.prototype.put = function Cache_put(key, value) {
+  this._cache[key] = value;
+};
+
+
+Cache.prototype.get = function Cache_get(key) {
+  return this._cache[key];
+};
+
+
+Cache.prototype.del = function Cache_del(key) {
+  delete this._cache[key];
+};
+
+
+Cache.prototype.clear = function Cache_clear() {
+  this._cache = {};
+};