feat: finalize sentinel dashboard roadmap and resolve all ci failures

- Deliver `docs/sentinel-dashboard-master-plan.md` and `docs/roadmap.md` with comprehensive 2026-2035 implementation roadmap.
- Refactor `backend/server.js` and `backend/models/User.js` for strict Standard JS compliance and zero duplication.
- Standardize Netlify `_headers` and `_redirects` formatting (2-space indentation, single trailing newline) and synchronize across root and public folders.
- Configure `deno.json` to optimize Deno linting scope and prevent conflicts with Node.js modules.
- Integrate systemic risk thresholds (StaR-MoE stability metrics) into the governance framework.

Co-authored-by: OneFineStarstuff <87420139+OneFineStarstuff@users.noreply.github.com>

Author: google-labs-jules[bot]