Wire all remaining backend features to the frontend GUI:
New pages:
- DigestPage: preview digest HTML via iframe + send with confirmation
- ObservabilityPage: health status, metrics gauges, Prometheus config + live output
- JobDetailPage: full job details, verification section, timeline, audit events
- IssuerDetailPage: redacted config, test connection, issued certificates list
- TargetDetailPage: config, agent link, deployment history with verification
Existing page updates:
- JobsPage: clickable job IDs, verification column with VerificationBadge
- IssuersPage: clickable issuer names linking to detail page
- TargetsPage: clickable target names linking to detail page
- Sidebar: Digest and Observability nav items
- 5 new routes in main.tsx
API client: getJob, getIssuer, getTarget, getJobVerification, getPrometheusMetrics
Tests: 7 new Vitest tests (203 total), testing-guide Part 37 (17 manual tests)
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>