Add a health‑check endpoint for container orchestration

[kael-developer]

Context

Problem
Kubernetes or other orchestrators have no way to verify that the SDLC service is healthy; missing liveness/readiness probes can cause downtime or slow recovery.

Solution
Expose a /healthz GET endpoint that returns HTTP 200 with JSON indicating overall status and sub‑checks (database connectivity, scheduler thread alive, message broker if used). Integrate this endpoint into the Dockerfile with a HEALTHCHECK directive.

Value
Enables automated health monitoring, rapid detection of failures, and smooth restarts in production environments.

Implementation notes
In the FastAPI app, add a route that runs quick sanity checks (e.g., engine.is_running(), db.session.execute('SELECT 1')). Return { "status": "ok", "checks": { "db": true, "scheduler": true } }. Update the Dockerfile to include HEALTHCHECK --interval=30s --timeout=5s CMD curl -f http://localhost:8000/healthz || exit 1. Add unit tests for the health endpoint.
Priority: P1

Implementation summary

We need to add healthHandler function above maybe after imports. Need to import net/http and encoding/json already imported. Already have net/http imported. At top imports line 3 included net/http. Good.

Add function before main or after generateID. Let's add after generateID for readability.

We need to edit file inserting new function. Use edit_file with context near end. Provide old snippet unique: maybe the closing brace of file. Let's open last few lines.

Closes #85