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/framer-motion/dist/es/utils/time-conversion.mjs

@@ -0,0 +1,10 @@
+/**
+ * Converts seconds to milliseconds
+ *
+ * @param seconds - Time in seconds.
+ * @return milliseconds - Converted time in milliseconds.
+ */
+const secondsToMilliseconds = (seconds) => seconds * 1000;
+const millisecondsToSeconds = (milliseconds) => milliseconds / 1000;
+
+export { millisecondsToSeconds, secondsToMilliseconds };