[Security] Enable Dependency graph so Dependabot alerts/updates run on this repo

[PAMulligan]

Summary

During the Wk 2 dependency + security sweep, Dependabot alerts could not be reviewed for this repo because the Dependency graph is disabled. With it off, Dependabot cannot surface vulnerability alerts or open automated security/update PRs, so this repo is effectively excluded from the weekly sweep.

Why this is filed rather than fixed in the sweep

Enabling the Dependency graph is a repository settings/access-control change. Per policy, settings/permission changes are not made automatically during the sweep — they are flagged for a maintainer to action.

Proposed work

• A maintainer enables Dependency graph under Settings → Advanced Security (or Code security & analysis).
• Enable Dependabot alerts and Dependabot security updates.
• Re-run the dependency sweep on this repo once alerts populate.

Notes

Surfaced during the weekly PMDS dependency + security sweep (Wk 2). No code or settings were changed by the sweep.