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/regjsgen/package.json

@@ -0,0 +1,40 @@
+{
+  "name": "regjsgen",
+  "version": "0.8.0",
+  "description": "Generate regular expressions from regjsparser’s AST.",
+  "homepage": "https://github.com/bnjmnt4n/regjsgen",
+  "main": "regjsgen.js",
+  "keywords": [
+    "ast",
+    "generate",
+    "regex",
+    "regexp",
+    "regular expressions"
+  ],
+  "license": "MIT",
+  "author": {
+    "name": "Benjamin Tan",
+    "url": "https://ofcr.se/"
+  },
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/bnjmnt4n/regjsgen.git"
+  },
+  "bugs": "https://github.com/bnjmnt4n/regjsgen/issues",
+  "files": [
+    "LICENSE-MIT.txt",
+    "regjsgen.js"
+  ],
+  "scripts": {
+    "test": "node tests/tests.js",
+    "coverage": "nyc --reporter=html npm test",
+    "report-coverage": "nyc --reporter=lcov npm test && codecov",
+    "update-fixtures": "node tests/update-fixtures.js"
+  },
+  "devDependencies": {
+    "codecov": "^3.8.3",
+    "nyc": "^15.1.0",
+    "regjsparser": "^0.10.0",
+    "request": "^2.88.2"
+  }
+}