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/redent/index.d.ts

@@ -0,0 +1,27 @@
+import {Options as IndentStringOptions} from 'indent-string';
+
+declare namespace redent {
+	type Options = IndentStringOptions;
+}
+
+/**
+[Strip redundant indentation](https://github.com/sindresorhus/strip-indent) and [indent the string](https://github.com/sindresorhus/indent-string).
+
+@param string - The string to normalize indentation.
+@param count - How many times you want `options.indent` repeated. Default: `0`.
+
+@example
+```
+import redent = require('redent');
+
+redent('\n  foo\n    bar\n', 1);
+//=> '\n foo\n   bar\n'
+```
+*/
+declare function redent(
+	string: string,
+	count?: number,
+	options?: redent.Options
+): string;
+
+export = redent;