fix: use vite-plugin-symfony Stimulus loader and wrap react_component in div

The @symfony/stimulus-bundle loader generates an empty controllers.js,
so Stimulus controllers from controllers.json (including ux-react) were
never registered. Switching to vite-plugin-symfony/stimulus/helpers
uses the virtual:symfony/controllers module that properly reads
controllers.json. Also wrap react_component() output in a <div> since
it only renders data-attributes, not a full HTML element.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

package.json

@@ -15,6 +15,8 @@
     "react-dom": "^19.0"
   },
   "devDependencies": {
+    "@symfony/stimulus-bridge": "^3.2.0 || ^4.0.0",
+    "@symfony/ux-turbo": "file:vendor/symfony/ux-turbo/assets",
     "@vitejs/plugin-react-swc": "^4.3.0",
     "vite": "^6.0",
     "vite-plugin-symfony": "^8.0"