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/object-inspect/example/all.js

@@ -0,0 +1,23 @@
+'use strict';
+
+var inspect = require('../');
+var Buffer = require('safer-buffer').Buffer;
+
+var holes = ['a', 'b'];
+holes[4] = 'e';
+holes[6] = 'g';
+
+var obj = {
+    a: 1,
+    b: [3, 4, undefined, null],
+    c: undefined,
+    d: null,
+    e: {
+        regex: /^x/i,
+        buf: Buffer.from('abc'),
+        holes: holes
+    },
+    now: new Date()
+};
+obj.self = obj;
+console.log(inspect(obj));