Feature unit FU-113 testing

[markmhendrickson]

Extend the entities data model with user scoping and merge tracking to enable privacy-first, deterministic entity management and prepare for merge functionality.

This PR implements Feature Unit FU-113, establishing user-scoped entities and merge tracking across the data model and application logic. This is crucial for ensuring data privacy and enabling deterministic entity management. Although the code changes are complete for the feature, automated tests failed because the Supabase CLI project was not linked, preventing database migrations from being applied and thus causing schema-dependent test failures.

---

 

[cursor]

Cursor Agent can help with this pull request. Just @cursor in comments and I'll start working on changes in this branch.
_{Learn more about Cursor Agents}