feat(web): persist CT-CVE connection status

[simonjcarr]

Summary

• add durable org-scoped CT-CVE connection status persisted in system_config
• return persisted status from signed connection health checks
• update finding ingest and inventory push flows to record connector success/error timestamps
• update migration plan and progress notes for Phase 9

Validation

• pnpm install --frozen-lockfile
• node --experimental-strip-types --test lib/integrations/ct-cve/connection-status.test.mjs lib/integrations/ct-cve/inventory-export.test.mjs lib/integrations/ct-cve/finding-ingest.test.mjs
• npm run type-check
• npm run db:validate
• npm run lint -- app/api/integrations/ct-cve/v1/connection-health/route.ts app/api/integrations/ct-cve/v1/finding-batches/route.ts lib/integrations/ct-cve/connection-status.ts lib/integrations/ct-cve/inventory-export.ts
• npm run test:unit

Remaining Phase 9 work: automated CT-CVE inventory push scheduling.