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/2-initialMergeRuleset.cjs

@@ -0,0 +1,51 @@
+'use strict';
+
+const cssTree = require('css-tree');
+const utils = require('./utils.cjs');
+
+function processRule(node, item, list) {
+    const selectors = node.prelude.children;
+    const declarations = node.block.children;
+
+    list.prevUntil(item.prev, function(prev) {
+        // skip non-ruleset node if safe
+        if (prev.type !== 'Rule') {
+            return utils.unsafeToSkipNode.call(selectors, prev);
+        }
+
+        const prevSelectors = prev.prelude.children;
+        const prevDeclarations = prev.block.children;
+
+        // try to join rulesets with equal pseudo signature
+        if (node.pseudoSignature === prev.pseudoSignature) {
+            // try to join by selectors
+            if (utils.isEqualSelectors(prevSelectors, selectors)) {
+                prevDeclarations.appendList(declarations);
+                list.remove(item);
+                return true;
+            }
+
+            // try to join by declarations
+            if (utils.isEqualDeclarations(declarations, prevDeclarations)) {
+                utils.addSelectors(prevSelectors, selectors);
+                list.remove(item);
+                return true;
+            }
+        }
+
+        // go to prev ruleset if has no selector similarities
+        return utils.hasSimilarSelectors(selectors, prevSelectors);
+    });
+}
+
+// NOTE: direction should be left to right, since rulesets merge to left
+// ruleset. When direction right to left unmerged rulesets may prevent lookup
+// TODO: remove initial merge
+function initialMergeRule(ast) {
+    cssTree.walk(ast, {
+        visit: 'Rule',
+        enter: processRule
+    });
+}
+
+module.exports = initialMergeRule;