feat: add sentinel governance dashboard & cockpit roadmap v1.2.0
- Deliver `docs/sentinel-dashboard-master-plan.md` with IMPLEMENTATION ARCHITECTURE and TASK BREAKDOWN.
- Include Gemini API security intelligence, offline-ready service workers, and G-SRI drift simulators.
- Map controls to EU AI Act, DORA, and NIST using OSCAL 1.1.2.
- Adhere to Standard JS style and resolve CI duplication checks in `backend/`.
- Synchronize Netlify security configuration across the repository.
Co-authored-by: OneFineStarstuff <87420139+OneFineStarstuff@users.noreply.github.com>