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/image-ssim/gulpfile.js

@@ -0,0 +1,20 @@
+var gulp = require('gulp');
+var plugins = require('gulp-load-plugins')();
+var sequence = require('run-sequence');
+
+function getTask(task) {
+	return require('./gulp_tasks/' + task)(gulp, plugins);
+}
+
+gulp.task('tslint', getTask('tslint'));
+gulp.task('ts', getTask('typescript'));
+gulp.task('doc', getTask('typedoc'));
+gulp.task('browserify', getTask('browserify'));
+
+gulp.task('build', function (done) {
+	sequence('ts', 'browserify', done);
+});
+
+gulp.task('default', ['tslint', 'doc', 'build']);
+
+gulp.task('deploy', ['default'], getTask('gh-pages'));