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/@jridgewell/trace-mapping/src/resolve.ts

@@ -0,0 +1,16 @@
+import resolveUri from '@jridgewell/resolve-uri';
+import stripFilename from './strip-filename';
+
+type Resolve = (source: string | null) => string;
+export default function resolver(
+  mapUrl: string | null | undefined,
+  sourceRoot: string | undefined,
+): Resolve {
+  const from = stripFilename(mapUrl);
+  // The sourceRoot is always treated as a directory, if it's not empty.
+  // https://github.com/mozilla/source-map/blob/8cb3ee57/lib/util.js#L327
+  // https://github.com/chromium/chromium/blob/da4adbb3/third_party/blink/renderer/devtools/front_end/sdk/SourceMap.js#L400-L401
+  const prefix = sourceRoot ? sourceRoot + '/' : '';
+
+  return (source) => resolveUri(prefix + (source || ''), from);
+}