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/fresh/package.json

@@ -0,0 +1,46 @@
+{
+  "name": "fresh",
+  "description": "HTTP response freshness testing",
+  "version": "0.5.2",
+  "author": "TJ Holowaychuk <tj@vision-media.ca> (http://tjholowaychuk.com)",
+  "contributors": [
+    "Douglas Christopher Wilson <doug@somethingdoug.com>",
+    "Jonathan Ong <me@jongleberry.com> (http://jongleberry.com)"
+  ],
+  "license": "MIT",
+  "keywords": [
+    "fresh",
+    "http",
+    "conditional",
+    "cache"
+  ],
+  "repository": "jshttp/fresh",
+  "devDependencies": {
+    "beautify-benchmark": "0.2.4",
+    "benchmark": "2.1.4",
+    "eslint": "3.19.0",
+    "eslint-config-standard": "10.2.1",
+    "eslint-plugin-import": "2.7.0",
+    "eslint-plugin-markdown": "1.0.0-beta.6",
+    "eslint-plugin-node": "5.1.1",
+    "eslint-plugin-promise": "3.5.0",
+    "eslint-plugin-standard": "3.0.1",
+    "istanbul": "0.4.5",
+    "mocha": "1.21.5"
+  },
+  "files": [
+    "HISTORY.md",
+    "LICENSE",
+    "index.js"
+  ],
+  "engines": {
+    "node": ">= 0.6"
+  },
+  "scripts": {
+    "bench": "node benchmark/index.js",
+    "lint": "eslint --plugin markdown --ext js,md .",
+    "test": "mocha --reporter spec --bail --check-leaks test/",
+    "test-cov": "istanbul cover node_modules/mocha/bin/_mocha -- --reporter dot --check-leaks test/",
+    "test-travis": "istanbul cover node_modules/mocha/bin/_mocha --report lcovonly -- --reporter spec --check-leaks test/"
+  }
+}