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/tmpl/lib/tmpl.js

@@ -0,0 +1,17 @@
+var INTERPOLATE = /{([^{]+?)}/g
+
+module.exports = function(str, data) {
+  var tmpl = 'var __p=[],print=function(){__p.push.apply(__p,arguments);};' +
+    'with(obj||{}){__p.push(\'' +
+    str.replace(/\\/g, '\\\\')
+       .replace(/'/g, "\\'")
+       .replace(INTERPOLATE, function(match, code) {
+         return "'," + code.replace(/\\'/g, "'") + ",'"
+       })
+       .replace(/\r/g, '\\r')
+       .replace(/\n/g, '\\n')
+       .replace(/\t/g, '\\t')
+       + "');}return __p.join('');"
+  var func = new Function('obj', tmpl)
+  return data ? func(data) : func
+}