fix(distributed): worker container healthcheck always unhealthy

The Dockerfile's HEALTHCHECK probes http://localhost:8080/readyz, which
is the OpenAI API server port. When the same image runs as a worker, it
listens on the gRPC base port (50051) and an HTTP file transfer server
on port-1 (50050) — nothing on 8080 — so docker always reports the
container as unhealthy.

Add unauthenticated /readyz and /healthz endpoints to the worker's HTTP
file transfer server, and override HEALTHCHECK_ENDPOINT for worker-1 in
the distributed compose file. Disable the healthcheck for agent-worker
since it is NATS-only and exposes no HTTP server.

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>
Assisted-by: claude-code:claude-opus-4-7
Signed-off-by: Ettore Di Giacinto <mudler@localai.io>