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/cssom/lib/CSSConditionRule.js

@@ -0,0 +1,25 @@
+//.CommonJS
+var CSSOM = {
+  CSSRule: require("./CSSRule").CSSRule,
+  CSSGroupingRule: require("./CSSGroupingRule").CSSGroupingRule
+};
+///CommonJS
+
+
+/**
+ * @constructor
+ * @see https://www.w3.org/TR/css-conditional-3/#the-cssconditionrule-interface
+ */
+CSSOM.CSSConditionRule = function CSSConditionRule() {
+  CSSOM.CSSGroupingRule.call(this);
+  this.cssRules = [];
+};
+
+CSSOM.CSSConditionRule.prototype = new CSSOM.CSSGroupingRule();
+CSSOM.CSSConditionRule.prototype.constructor = CSSOM.CSSConditionRule;
+CSSOM.CSSConditionRule.prototype.conditionText = ''
+CSSOM.CSSConditionRule.prototype.cssText = ''
+
+//.CommonJS
+exports.CSSConditionRule = CSSOM.CSSConditionRule;
+///CommonJS