docs: record final validation completion pass

[hyeokjun32]

Summary

• Added a final portfolio-grade validation completion checkpoint document.
• Linked the completion pass from README and the pipeline status document.
• Synchronized Obsidian source-of-truth docs to mark the local-first validation workflow complete while keeping production SaaS as future work.

Validation

• poetry run python3 -m pytest -q

Impact

• Clarifies the current project boundary for portfolio/interview use.
• Separates completed local-first validation workflow evidence from future production SaaS infrastructure.

Notes

• No production worker, DB, queue, upload, auth, billing, or cloud dashboard behavior was added.