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/_baseClamp.js

@@ -0,0 +1,22 @@
+/**
+ * The base implementation of `_.clamp` which doesn't coerce arguments.
+ *
+ * @private
+ * @param {number} number The number to clamp.
+ * @param {number} [lower] The lower bound.
+ * @param {number} upper The upper bound.
+ * @returns {number} Returns the clamped number.
+ */
+function baseClamp(number, lower, upper) {
+  if (number === number) {
+    if (upper !== undefined) {
+      number = number <= upper ? number : upper;
+    }
+    if (lower !== undefined) {
+      number = number >= lower ? number : lower;
+    }
+  }
+  return number;
+}
+
+module.exports = baseClamp;