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/lodash/_baseSlice.js

@@ -0,0 +1,31 @@
+/**
+ * The base implementation of `_.slice` without an iteratee call guard.
+ *
+ * @private
+ * @param {Array} array The array to slice.
+ * @param {number} [start=0] The start position.
+ * @param {number} [end=array.length] The end position.
+ * @returns {Array} Returns the slice of `array`.
+ */
+function baseSlice(array, start, end) {
+  var index = -1,
+      length = array.length;
+
+  if (start < 0) {
+    start = -start > length ? 0 : (length + start);
+  }
+  end = end > length ? length : end;
+  if (end < 0) {
+    end += length;
+  }
+  length = start > end ? 0 : ((end - start) >>> 0);
+  start >>>= 0;
+
+  var result = Array(length);
+  while (++index < length) {
+    result[index] = array[index + start];
+  }
+  return result;
+}
+
+module.exports = baseSlice;