fix(uploads): bundling AsyncAPI multi-fichiers sans appel réseau

- Ajout @asyncapi/bundler@0.9.0 en dépendance locale
- Remplace execFile('asyncapi bundle') par l'API programmatique
- redocly bundle conservé pour OpenAPI (pas de pb réseau)

Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

back/package.json

@@ -29,6 +29,7 @@
     "class-validator": "^0.14.0",
     "class-transformer": "^0.5.0",
     "@asyncapi/cli": "6.0.0",
+    "@asyncapi/bundler": "0.9.0",
     "@asyncapi/generator": "3.0.1",
     "@asyncapi/html-template": "3.5.6",
     "@redocly/cli": "latest"