feat(models): add external safety benchmark metadata

[emilieschario]

Summary

• Add optional external safety-score metadata to model catalog responses.
• Synchronize validated scores daily while preserving existing benchmark data.

Verification

Manual live-provider verification has not been performed. This PR remains a draft pending that validation.

Visual Changes

N/A

Reviewer Notes

• 131 focused automated tests passed, including database integration tests.
• Web and database lint and typechecks passed.
• Test fixtures are synthetic; no credentials or live response samples are included.