feat(monitoring): deploy Prometheus + Grafana stack via Docker

- prometheus.yml: scrapes node, postgres, redis, nexus-pos, nexus-quart
- docker-compose.monitoring.yml: Prometheus, Grafana, node-exporter,
  postgres-exporter, redis-exporter
- Grafana auto-provisions Prometheus datasource
- Access: Grafana :3001 (admin/nexus2026), Prometheus :9090

docker/docker-compose.monitoring.yml

@@ -0,0 +1,60 @@
+version: "3.8"
+
+services:
+  prometheus:
+    image: prom/prometheus:v2.51.0
+    container_name: nexus-prometheus
+    restart: unless-stopped
+    ports:
+      - "9090:9090"
+    volumes:
+      - ./prometheus:/etc/prometheus
+      - prometheus-data:/prometheus
+    command:
+      - '--config.file=/etc/prometheus/prometheus.yml'
+      - '--storage.tsdb.path=/prometheus'
+      - '--web.console.libraries=/usr/share/prometheus/console_libraries'
+      - '--web.console.templates=/usr/share/prometheus/consoles'
+      - '--web.enable-lifecycle'
+
+  grafana:
+    image: grafana/grafana:10.4.1
+    container_name: nexus-grafana
+    restart: unless-stopped
+    ports:
+      - "3001:3000"
+    volumes:
+      - grafana-data:/var/lib/grafana
+      - ./grafana/provisioning:/etc/grafana/provisioning
+    environment:
+      - GF_SECURITY_ADMIN_USER=admin
+      - GF_SECURITY_ADMIN_PASSWORD=nexus2026
+      - GF_USERS_ALLOW_SIGN_UP=false
+
+  node-exporter:
+    image: prom/node-exporter:v1.7.0
+    container_name: nexus-node-exporter
+    restart: unless-stopped
+    network_mode: host
+
+  postgres-exporter:
+    image: prometheuscommunity/postgres-exporter:v0.15.0
+    container_name: nexus-postgres-exporter
+    restart: unless-stopped
+    environment:
+      DATA_SOURCE_NAME: "postgresql://postgres@172.17.0.1:5432/nexus_autoparts?sslmode=disable"
+    ports:
+      - "9187:9187"
+
+  redis-exporter:
+    image: oliver006/redis_exporter:v1.58.0
+    container_name: nexus-redis-exporter
+    restart: unless-stopped
+    environment:
+      REDIS_ADDR: "redis://172.17.0.1:6379"
+    ports:
+      - "9121:9121"
+
+volumes:
+  prometheus-data:
+  grafana-data: