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/selfsigned/.jshintrc

@@ -0,0 +1,39 @@
+{
+  "camelcase": false,
+  "curly": false,
+
+  "node": true,
+  "esnext": true,
+  "bitwise": true,
+  "eqeqeq": true,
+  "immed": true,
+  "indent": 2,
+  "latedef": true,
+  "newcap": true,
+  "noarg": true,
+  "regexp": true,
+  "undef": true,
+  "strict": false,
+  "smarttabs": true,
+  "expr": true,
+
+  "evil": true,
+  "browser": true,
+  "regexdash": true,
+  "wsh": true,
+  "trailing": true,
+  "sub": true,
+  "unused": true,
+  "laxcomma": true,
+
+  "globals": {
+    "after": false,
+    "before": false,
+    "afterEach": false,
+    "beforeEach": false,
+    "describe": false,
+    "it": false,
+    "DOMParser": true,
+    "XMLSerializer": true
+  }
+}