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/@sentry/utils/esm/env.js

@@ -0,0 +1,23 @@
+/*
+ * This module exists for optimizations in the build process through rollup and terser.  We define some global
+ * constants, which can be overridden during build. By guarding certain pieces of code with functions that return these
+ * constants, we can control whether or not they appear in the final bundle. (Any code guarded by a false condition will
+ * never run, and will hence be dropped during treeshaking.) The two primary uses for this are stripping out calls to
+ * `logger` and preventing node-related code from appearing in browser bundles.
+ *
+ * Attention:
+ * This file should not be used to define constants/flags that are intended to be used for tree-shaking conducted by
+ * users. These fags should live in their respective packages, as we identified user tooling (specifically webpack)
+ * having issues tree-shaking these constants across package boundaries.
+ * An example for this is the __SENTRY_DEBUG__ constant. It is declared in each package individually because we want
+ * users to be able to shake away expressions that it guards.
+ */
+/**
+ * Figures out if we're building a browser bundle.
+ *
+ * @returns true if this is a browser bundle build.
+ */
+export function isBrowserBundle() {
+    return typeof __SENTRY_BROWSER_BUNDLE__ !== 'undefined' && !!__SENTRY_BROWSER_BUNDLE__;
+}
+//# sourceMappingURL=env.js.map