Add health check endpoints for k8s liveness and readiness probes

[treblereel]

Context

Part of epic #1 — Build production-ready REST microservice with k8s deployment on top of casehub-engine. Kubernetes needs liveness and readiness probes to manage pod lifecycle and traffic routing.

What

Configure health check endpoints using Quarkus SmallRye Health:

• /q/health/live — liveness probe (is JVM running?)
• /q/health/ready — readiness probe (can service handle traffic?)
• Custom readiness checks for database connectivity and case engine initialization

Acceptance Criteria

• Liveness probe returns 200 when application is running (JVM alive)
• Readiness probe returns 200 when database is reachable and case engine is initialized
• Readiness probe returns 503 during startup or when database is unreachable
• Custom readiness check verifies CaseEngine is initialized and ready
• Custom readiness check verifies database connection pool is healthy
• Health check responses include component details (database: UP/DOWN, engine: UP/DOWN)
• Integration tests verify health endpoints behavior and state transitions

Notes

• Use quarkus-smallrye-health extension
• Implement @Readiness check for database using datasource health check
• Implement @Readiness check for case engine initialization state
• Liveness should be simple (process alive), readiness should verify dependencies
• File paths: custom health check implementations in /health package

[mdproctor]

Related: #24 tracks the broader Quarkus-native developer experience epic (@CaseType, TaskDefinition sugar, live reload). Health checks are scoped here; that issue excludes them.