✨ feat(server): add /api/healthz endpoint with rich health info (#20)

Adds Kubernetes-style /api/healthz endpoint with status/version/uptime_seconds/timestamp.

Non-breaking — /api/health preserved. Includes unit test (passes locally) and BDD scenario (validated by CI).

Généré ~95% en autonomie par Mistral Vibe via workspace ICM ~/Work/Vibe/workspaces/healthz-feature/.

Co-authored-by: Gabriel Radureau <arcodange@gmail.com>
Co-committed-by: Gabriel Radureau <arcodange@gmail.com>

pkg/bdd/steps/steps.go

@@ -83,6 +83,7 @@ func InitializeAllSteps(ctx *godog.ScenarioContext, client *testserver.Client, s
 
 	// Health steps
 	ctx.Step(`^I request the health endpoint$`, sc.healthSteps.iRequestTheHealthEndpoint)
+	ctx.Step(`^I request the healthz endpoint$`, sc.healthSteps.iRequestTheHealthzEndpoint)
 	ctx.Step(`^the server is running$`, sc.healthSteps.theServerIsRunning)
 
 	// Auth steps
@@ -297,4 +298,6 @@ func InitializeAllSteps(ctx *godog.ScenarioContext, client *testserver.Client, s
 	ctx.Step(`^the response should be "{\\"([^"]*)":\\"([^"]*)"}"$`, sc.commonSteps.theResponseShouldBe)
 	ctx.Step(`^the response should contain error "([^"]*)"$`, sc.commonSteps.theResponseShouldContainError)
 	ctx.Step(`^the status code should be (\d+)$`, sc.commonSteps.theStatusCodeShouldBe)
+	ctx.Step(`^the response should be JSON with fields "([^"]*)"$`, sc.commonSteps.theResponseShouldBeJSONWithFields)
+	ctx.Step(`^the "([^"]*)" field should equal "([^"]*)"$`, sc.commonSteps.theFieldShouldEqual)
 }