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/yaml/util.js

@@ -0,0 +1,16 @@
+const util = require('./dist/util')
+
+exports.findPair = util.findPair
+exports.toJSON = util.toJSON
+exports.parseMap = util.parseMap
+exports.parseSeq = util.parseSeq
+
+exports.stringifyNumber = util.stringifyNumber
+exports.stringifyString = util.stringifyString
+exports.Type = util.Type
+
+exports.YAMLError = util.YAMLError
+exports.YAMLReferenceError = util.YAMLReferenceError
+exports.YAMLSemanticError = util.YAMLSemanticError
+exports.YAMLSyntaxError = util.YAMLSyntaxError
+exports.YAMLWarning = util.YAMLWarning