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/terser/bin/package.json

@@ -0,0 +1,10 @@
+{
+  "name": "bin",
+  "private": true,
+  "version": "1.0.0",
+  "main": "terser",
+  "type": "commonjs",
+  "author": "",
+  "license": "BSD-2-Clause",
+  "description": "A package to hold the Terser bin bundle as commonjs while keeping the rest of it ESM."
+}

node_modules/terser/bin/terser

@@ -0,0 +1,21 @@
+#!/usr/bin/env node
+
+"use strict";
+
+require("../tools/exit.cjs");
+
+try {
+    require("source-map-support").install();
+} catch (err) {}
+
+const fs = require("fs");
+const path = require("path");
+const program = require("commander");
+
+const packageJson = require("../package.json");
+const { _run_cli: run_cli } = require("..");
+
+run_cli({ program, packageJson, fs, path }).catch((error) => {
+    console.error(error);
+    process.exitCode = 1;
+});

node_modules/terser/bin/uglifyjs

@@ -0,0 +1,10 @@
+#!/usr/bin/env node
+// -*- js -*-
+/* eslint-env node */
+
+"use strict";
+
+process.stderr.write( "DEPRECATION WARNING: uglifyjs binary will soon be discontinued!\n");
+process.stderr.write("Please use \"terser\" instead.\n\n");
+
+require("./terser");