Harden production readiness

[im-anishraj]

Summary

• Renames the product surface to CampaignCue across the app/docs touched by this launch-hardening pass.
• Adds atomic monthly DM usage reservations and Redis Lua-based hourly DM reservations in the worker path.
• Adds worker heartbeat/alerts, /api/health, authenticated /diagnostics, token-refresh operational events, and an OperationalEvent migration.
• Adds Privacy, Terms, Data Deletion, and Meta App Review support pages plus production-readiness/audit/staging smoke docs.

Validation

• npm run db:generate
• npm run typecheck
• npm run lint
• npm test
• npm run build
• Browser smoke: /, /privacy, /terms, /data-deletion, /meta-review, and protected /diagnostics redirect to /login with zero console errors
• npm audit --omit=dev --audit-level=moderate still reports documented exceptions for current stable next/postcss and Prisma CLI tooling advisories

Closes #7