serve: bind to localhost by default (#706)

[Matir]

This defaults to having the docker container for the openhands server bind to localhost only, but also provides a flag that allows for the user to select any host/port to bind to:

# bind to all interfaces, port 8888
openhands server --bind=0.0.0.0:8888

# bind to all interfaces, port 3000 (default)
openhands server --bind=0.0.0.0

# bind to loopback, port 8888
openhands server --bind=127.0.0.1:8888

Tests:

make lint
Checking uv version...
uv version 0.11.10 meets requirements
Linting code with uv format...
uv run ruff check openhands_cli/ --fix
All checks passed!
Code linted successfully.

make test
(... output elided)
==================================== 1322 passed in 60.41s (0:01:00) =====================================
Tests completed.

[Matir]

This will fix the security issue in #706 .