feat: add end-to-end observability (metrics, health, mobile RUM, dashboards, alerts)

- Backend: OTel metrics via OTLP -> Alloy -> Prometheus (OTEL_METRICS_EXPORTER=otlp)
- New business metrics (src/metrics.js): searches, CIMA latency/errors, cache
  hits/misses, logins, rate-limits, pharmacy writes/links, push sent/failed,
  DB + Redis timings/errors, HTTP req count/duration, heartbeat
- Backend health endpoints /healthz and /readyz
- Mobile (Expo): Grafana Faro RUM via @grafana/faro-react-native
- redis/postgres exporters in docker-compose + Prometheus scrape jobs
- Grafana dashboards (backend, datastores, mobile RUM, overview)
- Prometheus alert rules (farmafinder_*) -> existing Alertmanager (Telegram)
- Design/spec saved to docs/superpowers/specs/

apps/frontend-mobile/.env.example

@@ -6,3 +6,8 @@ EXPO_PUBLIC_API_URL=http://localhost:3001/api
 
 # For production builds, update this to:
 # EXPO_PUBLIC_API_URL=https://api.yourdomain.com/api
+
+# Grafana Alloy OTLP/HTTP endpoint for Faro RUM (must be reachable from the
+# device — use a LAN IP / public hostname, NOT localhost).
+# Open router :4318 → srv84-macos:4318, or proxy /faro via Nginx Proxy Manager.
+EXPO_PUBLIC_FARO_URL=http://grafana.hacecalor.net:4318