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/core-js/internals/math-log10.js

@@ -0,0 +1,8 @@
+'use strict';
+var log = Math.log;
+var LOG10E = Math.LOG10E;
+
+// eslint-disable-next-line es/no-math-log10 -- safe
+module.exports = Math.log10 || function log10(x) {
+  return log(x) * LOG10E;
+};