fix(docs-generation): utiliser @asyncapi/generator en API programmatique

Remplace execFile('asyncapi') par l'API Node.js directe — aucun appel
réseau vers registry.npmjs.org, template résolu depuis node_modules local.

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/generator": "3.0.1",
     "@asyncapi/html-template": "3.5.6",
     "@redocly/cli": "latest"
   },