✨(agent) support Voxtral realtime as inference engine

The Kyutai open-source model turned out not to be production-ready:
it caused disruptions in the production environment, especially on
long-running meeting sessions.

Switch to the Voxtral realtime model, which looks like a
credible competitor and behaves much better in our setup.

For now, the code handling the Voxtral realtime API lives directly
in the project. It could be extracted into an open-source package
later.

See PR #1277 for the full details of the implementation, proposed
by @cameldev.

src/agents/pyproject.toml

@@ -12,6 +12,8 @@ dependencies = [
     "protobuf==6.33.6",
     "minio==7.2.20",
     "sentry-sdk==2.66.1",
+    "websockets==17.1",
+    "httpx==0.28.1",
 ]
 
 [project.optional-dependencies]