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/csso/cjs/restructure/3-disjoinRuleset.cjs

@@ -0,0 +1,46 @@
+'use strict';
+
+const cssTree = require('css-tree');
+
+function processRule(node, item, list) {
+    const selectors = node.prelude.children;
+
+    // generate new rule sets:
+    // .a, .b { color: red; }
+    // ->
+    // .a { color: red; }
+    // .b { color: red; }
+
+    // while there are more than 1 simple selector split for rulesets
+    while (selectors.head !== selectors.tail) {
+        const newSelectors = new cssTree.List();
+
+        newSelectors.insert(selectors.remove(selectors.head));
+
+        list.insert(list.createItem({
+            type: 'Rule',
+            loc: node.loc,
+            prelude: {
+                type: 'SelectorList',
+                loc: node.prelude.loc,
+                children: newSelectors
+            },
+            block: {
+                type: 'Block',
+                loc: node.block.loc,
+                children: node.block.children.copy()
+            },
+            pseudoSignature: node.pseudoSignature
+        }), item);
+    }
+}
+
+function disjoinRule(ast) {
+    cssTree.walk(ast, {
+        visit: 'Rule',
+        reverse: true,
+        enter: processRule
+    });
+}
+
+module.exports = disjoinRule;