- Add port and host fields to GatewayConfig with defaults (3000, 127.0.0.1)
- Enhanced apply_env_overrides() to support:
- ZEROCLAW_GATEWAY_PORT or PORT - Gateway server port
- ZEROCLAW_GATEWAY_HOST or HOST - Gateway bind address
- ZEROCLAW_TEMPERATURE - Default temperature (0.0-2.0)
- Add comprehensive tests for all new env var overrides
- Fix clippy warnings (is_multiple_of, too_many_lines)
Closes#45