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/cssstyle/lib/properties/flex.js

@@ -0,0 +1,45 @@
+'use strict';
+
+var shorthandParser = require('../parsers').shorthandParser;
+var shorthandSetter = require('../parsers').shorthandSetter;
+var shorthandGetter = require('../parsers').shorthandGetter;
+
+var shorthand_for = {
+  'flex-grow': require('./flexGrow'),
+  'flex-shrink': require('./flexShrink'),
+  'flex-basis': require('./flexBasis'),
+};
+
+var myShorthandSetter = shorthandSetter('flex', shorthand_for);
+
+module.exports.isValid = function isValid(v) {
+  return shorthandParser(v, shorthand_for) !== undefined;
+};
+
+module.exports.definition = {
+  set: function(v) {
+    var normalizedValue = String(v)
+      .trim()
+      .toLowerCase();
+
+    if (normalizedValue === 'none') {
+      myShorthandSetter.call(this, '0 0 auto');
+      return;
+    }
+    if (normalizedValue === 'initial') {
+      myShorthandSetter.call(this, '0 1 auto');
+      return;
+    }
+    if (normalizedValue === 'auto') {
+      this.removeProperty('flex-grow');
+      this.removeProperty('flex-shrink');
+      this.setProperty('flex-basis', normalizedValue);
+      return;
+    }
+
+    myShorthandSetter.call(this, v);
+  },
+  get: shorthandGetter('flex', shorthand_for),
+  enumerable: true,
+  configurable: true,
+};