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/pure-rand/lib/distribution/UnsafeUniformBigIntDistribution.js

@@ -0,0 +1,28 @@
+"use strict";
+exports.__esModule = true;
+exports.unsafeUniformBigIntDistribution = void 0;
+var SBigInt = typeof BigInt !== 'undefined' ? BigInt : undefined;
+function unsafeUniformBigIntDistribution(from, to, rng) {
+    var diff = to - from + SBigInt(1);
+    var MinRng = SBigInt(-0x80000000);
+    var NumValues = SBigInt(0x100000000);
+    var FinalNumValues = NumValues;
+    var NumIterations = 1;
+    while (FinalNumValues < diff) {
+        FinalNumValues *= NumValues;
+        ++NumIterations;
+    }
+    var MaxAcceptedRandom = FinalNumValues - (FinalNumValues % diff);
+    while (true) {
+        var value = SBigInt(0);
+        for (var num = 0; num !== NumIterations; ++num) {
+            var out = rng.unsafeNext();
+            value = NumValues * value + (SBigInt(out) - MinRng);
+        }
+        if (value < MaxAcceptedRandom) {
+            var inDiff = value % diff;
+            return inDiff + from;
+        }
+    }
+}
+exports.unsafeUniformBigIntDistribution = unsafeUniformBigIntDistribution;