Fix nginx-exporter: use host network mode for direct stub_status access

nginx-exporter couldn't reach host nginx via host.docker.internal
(connection timeout). Switch to network_mode: host so it can access
127.0.0.1:8888 directly. Prometheus scrapes via host.docker.internal
with extra_hosts mapping.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docker-compose.yml

@@ -298,6 +298,8 @@ services:
       - --config.file=/etc/prometheus/prometheus.yml
       - --storage.tsdb.retention.time=90d
       - --web.enable-lifecycle
+    extra_hosts:
+      - "host.docker.internal:host-gateway"
     restart: unless-stopped
 
   grafana:
@@ -372,9 +374,8 @@ services:
   nginx-exporter:
     image: nginx/nginx-prometheus-exporter:latest
     command:
-      - -nginx.scrape-uri=http://host.docker.internal:8888/nginx_status
-    extra_hosts:
-      - "host.docker.internal:host-gateway"
+      - -nginx.scrape-uri=http://127.0.0.1:8888/nginx_status
+    network_mode: host
     restart: unless-stopped
 
   blackbox-exporter:

monitoring/prometheus.yml

@@ -42,7 +42,7 @@ scrape_configs:
   # ── nginx ──────────────────────────────────────────────────────────
   - job_name: nginx
     static_configs:
-      - targets: ["nginx-exporter:9113"]
+      - targets: ["host.docker.internal:9113"]
 
   # ── Blackbox probes (HTTP endpoint monitoring) ─────────────────────
   - job_name: blackbox_http