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/CSSMediaRule.js

@@ -0,0 +1,53 @@
+//.CommonJS
+var CSSOM = {
+	CSSRule: require("./CSSRule").CSSRule,
+	CSSGroupingRule: require("./CSSGroupingRule").CSSGroupingRule,
+	CSSConditionRule: require("./CSSConditionRule").CSSConditionRule,
+	MediaList: require("./MediaList").MediaList
+};
+///CommonJS
+
+
+/**
+ * @constructor
+ * @see http://dev.w3.org/csswg/cssom/#cssmediarule
+ * @see http://www.w3.org/TR/DOM-Level-2-Style/css.html#CSS-CSSMediaRule
+ */
+CSSOM.CSSMediaRule = function CSSMediaRule() {
+	CSSOM.CSSConditionRule.call(this);
+	this.media = new CSSOM.MediaList();
+};
+
+CSSOM.CSSMediaRule.prototype = new CSSOM.CSSConditionRule();
+CSSOM.CSSMediaRule.prototype.constructor = CSSOM.CSSMediaRule;
+CSSOM.CSSMediaRule.prototype.type = 4;
+
+// https://opensource.apple.com/source/WebCore/WebCore-7611.1.21.161.3/css/CSSMediaRule.cpp
+Object.defineProperties(CSSOM.CSSMediaRule.prototype, {
+  "conditionText": {
+    get: function() {
+      return this.media.mediaText;
+    },
+    set: function(value) {
+      this.media.mediaText = value;
+    },
+    configurable: true,
+    enumerable: true
+  },
+  "cssText": {
+    get: function() {
+      var cssTexts = [];
+      for (var i=0, length=this.cssRules.length; i < length; i++) {
+        cssTexts.push(this.cssRules[i].cssText);
+      }
+      return "@media " + this.media.mediaText + " {" + cssTexts.join("") + "}";
+    },
+    configurable: true,
+    enumerable: true
+  }
+});
+
+
+//.CommonJS
+exports.CSSMediaRule = CSSOM.CSSMediaRule;
+///CommonJS