US-012 - Prometheus metrics and Grafana dashboards for all services

[Teboho66]

As a Platform Administrator, I want all services to emit Prometheus metrics and structured logs so that I can detect performance degradation and incidents within 2 minutes of occurrence.

Acceptance Criteria:

• All services expose /metrics endpoint
• Grafana dashboard shows P50, P95, P99 latency in real time
• Alert fires within 2 minutes of P99 exceeding 100ms
• Structured JSON logs emitted by every service

Traceability: NFR-O1, UC12
Story Points: 5
Priority: Medium | MoSCoW: Should-have