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/flat/cli.js

@@ -0,0 +1,42 @@
+#!/usr/bin/env node
+
+const fs = require('fs')
+const path = require('path')
+const readline = require('readline')
+
+const flat = require('./index')
+
+const filepath = process.argv.slice(2)[0]
+if (filepath) {
+  // Read from file
+  const file = path.resolve(process.cwd(), filepath)
+  fs.accessSync(file, fs.constants.R_OK) // allow to throw if not readable
+  out(require(file))
+} else if (process.stdin.isTTY) {
+  usage(0)
+} else {
+  // Read from newline-delimited STDIN
+  const lines = []
+  readline.createInterface({
+    input: process.stdin,
+    output: process.stdout,
+    terminal: false
+  })
+    .on('line', line => lines.push(line))
+    .on('close', () => out(JSON.parse(lines.join('\n'))))
+}
+
+function out (data) {
+  process.stdout.write(JSON.stringify(flat(data), null, 2))
+}
+
+function usage (code) {
+  console.log(`
+Usage:
+
+flat foo.json
+cat foo.json | flat
+`)
+
+  process.exit(code || 0)
+}