feat: bind to 127.0.0.1 by default instead of 0.0.0.0
Port bindings now default to localhost-only, preventing prediction
endpoints from being exposed to the entire network during development.
- Add HostIP field to command.Port struct (defaults to 127.0.0.1)
- Add --host flag to cog serve (default 127.0.0.1, use 0.0.0.0 to expose)
- Support host:port syntax in cog run -p (e.g. -p 0.0.0.0:8888)
- Bind cog predict/train to 127.0.0.1
- Update GetHostPortForContainer to match configured host IP
