Adds a Kubernetes-style healthz endpoint returning status, version,
uptime_seconds and timestamp. Non-breaking — /api/health is preserved.
- New route: GET /api/healthz
- New handler: handleHealthz with HealthzResponse struct
- New unit test: pkg/server/healthz_test.go (passes locally)
- New BDD scenario: features/health/health.feature
- BDD steps: pkg/bdd/steps/health_steps.go, common_steps.go
Note: BDD tests require Postgres and will be validated by CI.
🤖 Co-Authored-By: Mistral Vibe (devstral-2 / mistral-medium-3.5)
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
