[Infrastructure] Implement health check endpoints with dependency status reporting

[Penielka]

Description

Add /health (liveness) and /health/ready (readiness) endpoints that report the status of all dependencies: database connectivity, Redis connectivity, Stellar RPC reachability, IPFS node status, and disk space. These are critical for Kubernetes/container orchestration and load balancer health checks.

Definition of Done

• GET /health returns 200 if process is alive (liveness probe)
• GET /health/ready returns 200 only if all dependencies are healthy (readiness probe)
• Dependency checks: PostgreSQL, Redis, Stellar RPC, IPFS node
• Each dependency check has configurable timeout (default 5s)
• Response includes per-dependency status: { "database": "up", "redis": "up", ... }
• Cache dependency check results for 10 seconds to avoid thundering herd
• Endpoints excluded from rate limiting and request logging
• Docker HEALTHCHECK instruction added to Dockerfiles

Acceptance Criteria

1. curl /health returns 200 with {"status": "ok"}
2. curl /health/ready returns 200 when all deps are up, 503 when any dep is down
3. Response body shows per-dependency status for debugging
4. Kubernetes/docker-compose uses these for health checks

Files to Modify

• New file: backend/src/routes/health.ts — health check routes
• backend/src/index.ts — register health routes
• backend/src/config/redis.ts — add ping method
• backend/Dockerfile — add HEALTHCHECK instruction
• frontend/Dockerfile — add HEALTHCHECK instruction
• docker-compose.yml — add healthcheck configs
• backend/src/docs/openapi.ts — document health endpoints

[clintjeff2]

Hello, I have 6 years of experience working on tasks like this and handling similar challenges across backend, frontend, and smart-contract development. I have carefully read and fully understood the task requirements, and I am confident I can deliver a clean, efficient, and well-tested solution promptly. I always ensure high-quality implementation, maintainability, and adherence to best practices.

Pull request in 5 hours.