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/core-js/modules/esnext.math.seeded-prng.js

@@ -0,0 +1,36 @@
+'use strict';
+var $ = require('../internals/export');
+var anObject = require('../internals/an-object');
+var numberIsFinite = require('../internals/number-is-finite');
+var createIteratorConstructor = require('../internals/iterator-create-constructor');
+var createIterResultObject = require('../internals/create-iter-result-object');
+var InternalStateModule = require('../internals/internal-state');
+
+var SEEDED_RANDOM = 'Seeded Random';
+var SEEDED_RANDOM_GENERATOR = SEEDED_RANDOM + ' Generator';
+var SEED_TYPE_ERROR = 'Math.seededPRNG() argument should have a "seed" field with a finite value.';
+var setInternalState = InternalStateModule.set;
+var getInternalState = InternalStateModule.getterFor(SEEDED_RANDOM_GENERATOR);
+var $TypeError = TypeError;
+
+var $SeededRandomGenerator = createIteratorConstructor(function SeededRandomGenerator(seed) {
+  setInternalState(this, {
+    type: SEEDED_RANDOM_GENERATOR,
+    seed: seed % 2147483647
+  });
+}, SEEDED_RANDOM, function next() {
+  var state = getInternalState(this);
+  var seed = state.seed = (state.seed * 1103515245 + 12345) % 2147483647;
+  return createIterResultObject((seed & 1073741823) / 1073741823, false);
+});
+
+// `Math.seededPRNG` method
+// https://github.com/tc39/proposal-seeded-random
+// based on https://github.com/tc39/proposal-seeded-random/blob/78b8258835b57fc2100d076151ab506bc3202ae6/demo.html
+$({ target: 'Math', stat: true, forced: true }, {
+  seededPRNG: function seededPRNG(it) {
+    var seed = anObject(it).seed;
+    if (!numberIsFinite(seed)) throw new $TypeError(SEED_TYPE_ERROR);
+    return new $SeededRandomGenerator(seed);
+  }
+});