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/path-is-inside/package.json

@@ -0,0 +1,21 @@
+{
+    "name": "path-is-inside",
+    "description": "Tests whether one path is inside another path",
+    "keywords": ["path", "directory", "folder", "inside", "relative"],
+    "version": "1.0.2",
+    "author": "Domenic Denicola <d@domenic.me> (https://domenic.me)",
+    "license": "(WTFPL OR MIT)",
+    "repository": "domenic/path-is-inside",
+    "main": "lib/path-is-inside.js",
+    "files": [
+        "lib"
+    ],
+    "scripts": {
+        "test": "mocha",
+        "lint": "jshint lib"
+    },
+    "devDependencies": {
+        "jshint": "~2.3.0",
+        "mocha": "~1.15.1"
+    }
+}