Expand lint, CI, and dependency quality gates

[wilsonfreitas]

Context

CI runs unit tests, Ruff, mypy, and Sphinx, but integration tests are excluded from PR CI and Ruff only checks a small rule set. Dependency security auditing is not represented in CI.

Scope

Add incremental quality gates for scheduled integration tests, stricter Ruff rules, coverage threshold increases, and dependency vulnerability auditing.

Branching

Create the implementation branch from project-health-hardening and merge the fix back into project-health-hardening before any merge to main.

Acceptance Criteria

• Scheduled integration workflow exists or an equivalent documented strategy is added.
• Ruff rule expansion is incremental and does not create excessive churn.
• Dependency audit automation is added or documented.
• CI remains practical for contributors.

[wilsonfreitas]

Completed in PR #56 and merged into project-health-hardening.