Refactor moleg-api internals for maintainability

[tjdwls101010]

Summary

• split large public facade modules into private implementation packages while preserving public imports
• split large laws orchestration paths into domain helpers for bundle, authority, institutional, delegated criteria, and follow-up routing
• document CLI surface, shared default OC, and maintainer layout/size guardrails
• bump package version to 0.2.3 for release

Verification

• python3 -m compileall moleg_api tests -q
• python3 -m pytest -q -m 'not live'
• MOLEG_OC=chunghun1 python3 -m pytest -q -m live
• python3 -m moleg_api --help
• python3 -m moleg_api catalog
• python3 -m build
• python3 -m twine check dist/*
• wheel import outside repository with 27 CLI task command and shared OC assertions