Module 4: remote client skeleton

[Shuhan6017]

Summary

Add the Module 4 RemoteClient skeleton: push/pull method stubs
Add _parse_address with colon splitting, and alphabet and number confirmation (used for host and ports)
push/pull into the CLI (note: not entirely sure how it works, done with the help with AI)
Add tests against FakeObjectStore/`FakeCommitManager'

Validation

• [ X] scripts/quality-check.sh
• [ X] Manual testing, if applicable:

Checklist

• [ X] The change is focused and easy to review.
• [ X] Tests were added or updated for behavior changes.
• Documentation was updated for user-facing or setup changes.
• [ X] No secrets, generated artifacts, or local-only files are included.

Notes for Reviewers

Might not be applicable, but I wasn't aware of the pre-commit hooks, so there might be some missing commits.
I commented out ObjectStore/CommitManager . I'll have to double check what it is called with devs in module 1 & 3.
thus, the fallback wouldn't work.