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/

docker-compose.yml

@@ -38,6 +38,7 @@ services:
       OTEL_SERVICE_NAME: farmafinder-backend
       OTEL_EXPORTER_OTLP_ENDPOINT: http://host.docker.internal:4317
       OTEL_TRACES_EXPORTER: otlp
+      OTEL_METRICS_EXPORTER: otlp
       OTEL_LOGS_EXPORTER: otlp
       OTEL_RESOURCE_ATTRIBUTES: service.namespace=farmafinder
     volumes:
@@ -61,6 +62,28 @@ services:
     depends_on:
       - backend
 
+  # --- Observability exporters (scraped by the shared Prometheus on srv84-macos) ---
+  redis-exporter:
+    image: oliver006/redis_exporter:latest
+    restart: unless-stopped
+    ports:
+      - "9121:9121"
+    environment:
+      REDIS_ADDR: redis://redis:6379
+      REDIS_PASSWORD: ${REDIS_PASSWORD:-}
+    depends_on:
+      - redis
+
+  postgres-exporter:
+    image: prometheuscommunity/postgres-exporter:latest
+    restart: unless-stopped
+    ports:
+      - "9187:9187"
+    environment:
+      DATA_SOURCE_NAME: postgresql://farmafinder:${PG_PASSWORD:-change-me-in-production}@postgres:5432/farmafinder?sslmode=disable
+    depends_on:
+      - postgres
+
 volumes:
   backend_data:
   postgres_data: