Health endpoints /healthz and /readyz with dependency checks

[tayebmokni]

Summary

Expose Kubernetes-style health endpoints /healthz (liveness) and /readyz (readiness) on the Go API server. /readyz should verify Postgres and Redis (when configured) are reachable.

Design reference

• docs/00-architecture-overview.md §4 (System Topology)
• docs/00-architecture-overview.md §6 (Phasing — P0)

Acceptance criteria

• GET /healthz returns 200 with {"status":"ok"} regardless of dependencies
• GET /readyz returns 200 only when pgxpool.Ping() succeeds; 503 otherwise
• /readyz body lists checked dependencies with per-dep status
• Endpoints excluded from auth middleware and request logging spam
• Integration test: kill DB connection, /readyz returns 503; restore, returns 200
• Endpoints respond in under 100ms

Dependencies

#3

Complexity

XS