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/stylehacks/src/dictionary/browsers.js

@@ -0,0 +1,9 @@
+'use strict';
+const FF_2 = 'firefox 2';
+const IE_5_5 = 'ie 5.5';
+const IE_6 = 'ie 6';
+const IE_7 = 'ie 7';
+const IE_8 = 'ie 8';
+const OP_9 = 'opera 9';
+
+module.exports = { FF_2, IE_5_5, IE_6, IE_7, IE_8, OP_9 };

node_modules/stylehacks/src/dictionary/identifiers.js

@@ -0,0 +1,7 @@
+'use strict';
+const MEDIA_QUERY = 'media query';
+const PROPERTY = 'property';
+const SELECTOR = 'selector';
+const VALUE = 'value';
+
+module.exports = { MEDIA_QUERY, PROPERTY, SELECTOR, VALUE };

node_modules/stylehacks/src/dictionary/postcss.js

@@ -0,0 +1,6 @@
+'use strict';
+const ATRULE = 'atrule';
+const DECL = 'decl';
+const RULE = 'rule';
+
+module.exports = { ATRULE, DECL, RULE };

node_modules/stylehacks/src/dictionary/tags.js

@@ -0,0 +1,5 @@
+'use strict';
+const BODY = 'body';
+const HTML = 'html';
+
+module.exports = { BODY, HTML };