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

monitoring/prometheus/prometheus.yml

@@ -0,0 +1,34 @@
+global:
+  scrape_interval: 30s
+  evaluation_interval: 30s
+
+rule_files:
+  - /etc/prometheus/alerts.yml
+
+scrape_configs:
+  # The ERP API — /metrics is exposed by prometheus-fastapi-instrumentator
+  # (request rate, latency histogram, error counts). Reached over the
+  # erp_shared network the main compose also joins.
+  - job_name: erp-api
+    metrics_path: /metrics
+    static_configs:
+      - targets: ["api:8000"]
+
+  # Host-level metrics (CPU, RAM, disk, network).
+  - job_name: node
+    static_configs:
+      - targets: ["node-exporter:9100"]
+
+  # Per-container metrics (CPU, memory, restarts) for every container.
+  - job_name: cadvisor
+    static_configs:
+      - targets: ["cadvisor:8080"]
+
+  # App database metrics (connections, cache hit ratio, WAL, ...).
+  - job_name: postgres
+    static_configs:
+      - targets: ["postgres-exporter:9187"]
+
+  - job_name: prometheus
+    static_configs:
+      - targets: ["localhost:9090"]