feat(phase-2): workstream 7 — Prometheus + Grafana Monitoring

- Add prom-client 15; shared registry in src/metrics/registry.ts (7 metrics)
- HTTP request counter + duration histogram via metricsMiddleware
- DB query duration histogram wrapping pg Pool.query
- Redis command duration histogram via typed instrumentRedisMethod wrapper
- agentidp_tokens_issued_total in OAuth2Service
- agentidp_agents_registered_total in AgentService
- GET /metrics unauthenticated endpoint (Prometheus text format)
- docker-compose.monitoring.yml overlay (Prometheus + Grafana)
- Grafana auto-provisioned datasource + pre-built AgentIdP dashboard
- docs/devops/operations.md monitoring section added
- 36/36 unit tests passing, 100% coverage on new metrics code
- Fix pre-existing unused import in tests/integration/agents.test.ts

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

package.json

@@ -15,6 +15,7 @@
     "format": "prettier --write src/**/*.ts"
   },
   "dependencies": {
+    "@open-policy-agent/opa-wasm": "^1.10.0",
     "bcryptjs": "^2.4.3",
     "cors": "^2.8.5",
     "dotenv": "^16.4.5",
@@ -27,6 +28,7 @@
     "pg": "^8.11.3",
     "pino": "^8.19.0",
     "pino-http": "^9.0.0",
+    "prom-client": "^15.1.3",
     "redis": "^4.6.13",
     "uuid": "^9.0.1"
   },