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/which/package.json

@@ -0,0 +1,30 @@
+{
+  "author": "Isaac Z. Schlueter <i@izs.me> (http://blog.izs.me)",
+  "name": "which",
+  "description": "Like which(1) unix command. Find the first instance of an executable in the PATH.",
+  "version": "1.3.1",
+  "repository": {
+    "type": "git",
+    "url": "git://github.com/isaacs/node-which.git"
+  },
+  "main": "which.js",
+  "bin": "./bin/which",
+  "license": "ISC",
+  "dependencies": {
+    "isexe": "^2.0.0"
+  },
+  "devDependencies": {
+    "mkdirp": "^0.5.0",
+    "rimraf": "^2.6.2",
+    "tap": "^12.0.1"
+  },
+  "scripts": {
+    "test": "tap test/*.js --cov",
+    "changelog": "bash gen-changelog.sh",
+    "postversion": "npm run changelog && git add CHANGELOG.md && git commit -m 'update changelog - '${npm_package_version}"
+  },
+  "files": [
+    "which.js",
+    "bin/which"
+  ]
+}