fix: expose Docker Hugo server

[kevinten10]

Summary

• publish the Hugo server container port when scripts/hugo.sh falls back to Docker
• preserve localhost-only binding by default and all-interface binding for make dev-all
• add a behavioral regression test for custom host and port mappings
• make shellcheck validation clean

Verification

• 14 Node tests pass
• Hugo 0.145.0 production build passes, producing 244 Chinese and 45 English pages
• make link-check crawls 298 rendered links successfully through the Docker fallback
• shellcheck and sh -n pass
• README and contribution links pass