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/safer-buffer/package.json

@@ -0,0 +1,34 @@
+{
+  "name": "safer-buffer",
+  "version": "2.1.2",
+  "description": "Modern Buffer API polyfill without footguns",
+  "main": "safer.js",
+  "scripts": {
+    "browserify-test": "browserify --external tape tests.js > browserify-tests.js && tape browserify-tests.js",
+    "test": "standard && tape tests.js"
+  },
+  "author": {
+    "name": "Nikita Skovoroda",
+    "email": "chalkerx@gmail.com",
+    "url": "https://github.com/ChALkeR"
+  },
+  "license": "MIT",
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/ChALkeR/safer-buffer.git"
+  },
+  "bugs": {
+    "url": "https://github.com/ChALkeR/safer-buffer/issues"
+  },
+  "devDependencies": {
+    "standard": "^11.0.1",
+    "tape": "^4.9.0"
+  },
+  "files": [
+    "Porting-Buffer.md",
+    "Readme.md",
+    "tests.js",
+    "dangerous.js",
+    "safer.js"
+  ]
+}