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/test/quoteStyle.js

@@ -0,0 +1,26 @@
+'use strict';
+
+var inspect = require('../');
+var test = require('tape');
+
+test('quoteStyle option', function (t) {
+    t['throws'](function () { inspect(null, { quoteStyle: false }); }, 'false is not a valid value');
+    t['throws'](function () { inspect(null, { quoteStyle: true }); }, 'true is not a valid value');
+    t['throws'](function () { inspect(null, { quoteStyle: '' }); }, '"" is not a valid value');
+    t['throws'](function () { inspect(null, { quoteStyle: {} }); }, '{} is not a valid value');
+    t['throws'](function () { inspect(null, { quoteStyle: [] }); }, '[] is not a valid value');
+    t['throws'](function () { inspect(null, { quoteStyle: 42 }); }, '42 is not a valid value');
+    t['throws'](function () { inspect(null, { quoteStyle: NaN }); }, 'NaN is not a valid value');
+    t['throws'](function () { inspect(null, { quoteStyle: function () {} }); }, 'a function is not a valid value');
+
+    t.equal(inspect('"', { quoteStyle: 'single' }), '\'"\'', 'double quote, quoteStyle: "single"');
+    t.equal(inspect('"', { quoteStyle: 'double' }), '"\\""', 'double quote, quoteStyle: "double"');
+
+    t.equal(inspect('\'', { quoteStyle: 'single' }), '\'\\\'\'', 'single quote, quoteStyle: "single"');
+    t.equal(inspect('\'', { quoteStyle: 'double' }), '"\'"', 'single quote, quoteStyle: "double"');
+
+    t.equal(inspect('`', { quoteStyle: 'single' }), '\'`\'', 'backtick, quoteStyle: "single"');
+    t.equal(inspect('`', { quoteStyle: 'double' }), '"`"', 'backtick, quoteStyle: "double"');
+
+    t.end();
+});