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/requireindex/test/lib/.also_private/private.txt

@@ -0,0 +1 @@
+barf

node_modules/requireindex/test/lib/Foo.js

@@ -0,0 +1,4 @@
+module.exports = {
+  l: function() { return "yes"; },
+  ls: function() { return "yep"; }
+};

node_modules/requireindex/test/lib/_private.js

@@ -0,0 +1,3 @@
+module.exports = function() {
+  return "ack";
+}

node_modules/requireindex/test/lib/bam.js

@@ -0,0 +1,4 @@
+module.exports = {
+  m: function() { return "ok"; },
+  n: require('./_private')
+};

node_modules/requireindex/test/lib/bar/f.js

@@ -0,0 +1,3 @@
+module.exports = function() {
+  return "yea";
+}

node_modules/requireindex/test/lib/bar/fed/again.js

@@ -0,0 +1,3 @@
+module.exports = function() {
+  return "again";
+}

node_modules/requireindex/test/lib/bar/fed/ignored.js

@@ -0,0 +1,3 @@
+module.exports = function() {
+  return "ignored";
+}

node_modules/requireindex/test/lib/bar/fed/index.js

@@ -0,0 +1 @@
+module.exports = require('../../../../')(__dirname, ['again', 'somemore'])

node_modules/requireindex/test/lib/bar/fed/somemore.js

@@ -0,0 +1,3 @@
+module.exports = function() {
+  return "somemore";
+}

node_modules/requireindex/test/lib/bar/fing.js

@@ -0,0 +1,3 @@
+module.exports = function() {
+  return "definitely";
+}

node_modules/requireindex/test/lib/bar/index.js

@@ -0,0 +1 @@
+module.exports = require('../../../')(__dirname)

node_modules/requireindex/test/lib/index.js

@@ -0,0 +1 @@
+module.exports = require('../../')(__dirname)

node_modules/requireindex/test/lib/not_javascript.txt

@@ -0,0 +1 @@
+asdf 1 2 / @ 123

node_modules/requireindex/test/test.js

@@ -0,0 +1,43 @@
+var Assert = require('assert');
+var Asserts = require('asserts');
+
+Asserts(function () {
+  var lib = require('./lib');
+
+  return {
+    "requireindex should": {
+      "properly include files parallel to index.js and maintain structure": function () {
+        Asserts.all.equal([
+          [lib.bam.m,            [], "ok"],
+          [lib.bar.f,            [], "yea"],
+          [lib.bar.fing,         [], 'definitely'],
+          [lib.Foo.l,            [], 'yes'],
+          [lib.Foo.ls,           [], 'yep'],
+          [lib.bam.n,            [], 'ack'],
+          [lib.bar.fed.again,    [], 'again'],
+          [lib.bar.fed.somemore, [], 'somemore']
+        ]);
+      },
+
+      "ignore _ prefixed files": function () {
+        Assert.equal(('_private' in lib), false);
+      },
+
+      "not include files not mentioned when second array argument is used": function () {
+        Assert.equal(('ignored' in lib.bar.fed), false);
+      },
+
+      "ignore non javascript files": function () {
+        Assert.equal(('not_javascript' in lib), false);
+      },
+
+      "sort files by lowercase alpha of the filename": function () {
+        Assert.equal(Object.keys(lib)[0], 'bam');
+      },
+      
+      "ignore dot files": function () {
+        Assert.equal(('.also_private' in lib), false);
+      },
+    }
+  };
+});