refactor(forge): migrate TODO service experiment

[fronzec]

Summary

• Move the TODO service into application-boundaries/todo-service.
• Update the root experiment catalog and canonical taxonomy links.
• Keep the PostgreSQL/Compose-backed experiment isolated from the remaining HTTP and storage migration slices.

Commit

• 7ebcbef refactor(forge): migrate TODO service experiment

Verification

• npm ci passed from the moved experiment.
• Targeted node --check commands passed for application, migration, model, utility, and test JavaScript.
• npm test -- --runInBand passed: 1 test suite and 1 test.
• All 22 moved files were detected as R100 renames; no legacy path references remain.
• PostgreSQL/Compose runtime was not started.

Scope

The latest main includes the separately merged Terminal UI work. This PR does not modify terminal-ui or its worktree.