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/string-length/package.json

@@ -0,0 +1,45 @@
+{
+	"name": "string-length",
+	"version": "4.0.2",
+	"description": "Get the real length of a string - by correctly counting astral symbols and ignoring ansi escape codes",
+	"license": "MIT",
+	"repository": "sindresorhus/string-length",
+	"author": {
+		"name": "Sindre Sorhus",
+		"email": "sindresorhus@gmail.com",
+		"url": "https://sindresorhus.com"
+	},
+	"engines": {
+		"node": ">=10"
+	},
+	"scripts": {
+		"test": "xo && ava && tsd"
+	},
+	"files": [
+		"index.js",
+		"index.d.ts"
+	],
+	"keywords": [
+		"unicode",
+		"string",
+		"length",
+		"size",
+		"count",
+		"astral",
+		"symbol",
+		"surrogates",
+		"codepoints",
+		"ansi",
+		"escape",
+		"codes"
+	],
+	"dependencies": {
+		"char-regex": "^1.0.2",
+		"strip-ansi": "^6.0.0"
+	},
+	"devDependencies": {
+		"ava": "^3.1.0",
+		"tsd": "^0.11.0",
+		"xo": "^0.25.3"
+	}
+}