feat(monitoring): observability stack + app instrumentation

- /health/ready (DB+MinIO+Casdoor checks, webhook post-deploy gate),
  /metrics via prometheus-fastapi-instrumentator, Sentry/GlitchTip capture,
  X-Request-ID middleware + JSON access logging (PROCUREMENT_LOG_FORMAT)
- server-side analytics (OpenPanel Track API): login, quote lifecycle,
  receipts — fire-and-forget, disabled without env config
- monitoring/ compose project: GlitchTip(+pg), Prometheus(+alerts),
  Grafana(provisioned ERP dashboard), Loki+Promtail, node/postgres
  exporters, cAdvisor — mem-limited (~2.2GB), loopback admin UIs,
  separate from app deploys; erp_shared network for scraping
- frontend: @openpanel/web + @sentry/react (build-arg gated, no-op when
  unset), funnel events (login, wizard steps, quote submitted)
- compose: api healthcheck, observability env wiring, .env.example keys

.env.example

@@ -40,9 +40,27 @@ DEV_LOGIN_ENABLED=false
 # --- Deploy webhook (Gitea push → rebuild; see infra/deploy-webhook/) ---
 GITEA_WEBHOOK_SECRET=CHANGE_ME_long_random_webhook_secret
 
-# --- Monitoring stack (see monitoring/docker-compose.monitoring.yml) ---
+# --- Monitoring stack (see monitoring/README.md) ---
+# API log format for Loki ingestion ("text" locally, "json" in production)
+LOG_FORMAT=json
+# GlitchTip (error tracking). GLITCHTIP_HOST must be a public DNS name —
+# the browser SDK posts errors there.
+GLITCHTIP_SECRET_KEY=CHANGE_ME_random_django_secret
+GLITCHTIP_DOMAIN=https://errors.bennu-api-bahrestan.ir
+GLITCHTIP_HOST=errors.bennu-api-bahrestan.ir
+GLITCHTIP_DB_PASSWORD=CHANGE_ME_glitchtip_db_password
+GLITCHTIP_FROM_EMAIL=noreply@bennu-api-bahrestan.ir
+GLITCHTIP_EMAIL_URL=consolemail://
+# Grafana (dashboards) — UI is loopback-only (:3001) unless you add Traefik labels
+GRAFANA_ADMIN_PASSWORD=CHANGE_ME_grafana_password
+GRAFANA_ROOT_URL=http://localhost:3001/
+# OpenPanel (product analytics) — client id/secret from the OpenPanel project
+OPENPANEL_API_URL=http://openpanel-api:3333
 OPENPANEL_CLIENT_ID=
 OPENPANEL_CLIENT_SECRET=
+# Public origin of the OpenPanel dashboard/API the BROWSER talks to
+# (e.g. https://stats.bennu-api-bahrestan.ir — see monitoring/README.md)
+OPENPANEL_PUBLIC_URL=
+# Sentry/GlitchTip DSNs created in the GlitchTip UI after first boot
 SENTRY_DSN_BACKEND=
 SENTRY_DSN_FRONTEND=
-GRAFANA_ADMIN_PASSWORD=CHANGE_ME_grafana_password