feat: build operational console

[XonkelX]

Summary

Implements Phase 5: Operational Console.

Owner operations API

• cursor-paginated event stream with indexed filters and operational metrics
• event and delivery inspector with persisted attempt evidence, safe payloads, redacted request/response headers, response excerpts, retry explanations, and bidirectional replay lineage
• endpoint management for verification, pause/resume, subscription updates, and signing-secret rotation with one-time secret reveal
• overview and system-health summaries
• authenticated owner-session bootstrap
• CSRF-protected manual delivery replay with explicit confirmation in the console

Console

• authenticated owner console
• production overview
• production event stream and delivery inspector
• production endpoint management with recent health/failure metrics
• production system-health, quota, and guardrail views
• responsive/browser coverage for authenticated operational flows
• removal of obsolete Phase 1 operational fixtures

Operations and security

• bounded 30-day event and attempt retention
• replay-safe retention handling under concurrent replay creation
• sensitive response-header redaction before persistence and browser exposure
• Phase 5 query indexes and EXPLAIN QUERY PLAN coverage
• canonical operational guardrails surfaced through the API

Verification

• npm run format-check
• npm run lint
• npm run typecheck
• npm run test
• npm run build
• npm run check:cost
• npm audit --omit=dev
• npm run test:e2e
• git diff --check

GitHub Actions CI is green on the current PR head.