feat: export Caddy metrics to VictoriaMetrics

- Add caddyserver/caddy/v2/modules/caddytelemetry to Caddy build
- Add metrics endpoint on :9090/metrics (localhost only)
- Add vmagent scrape config for Caddy metrics

This enables monitoring Caddy traffic and performance in Grafana.

Author: bolotas-migas

caddy/Caddyfile.production

@@ -3,6 +3,13 @@
 	admin localhost:2019
 }
 
+# Enable telemetry module for Prometheus metrics
+(telemetry) {
+	telemetry {
+		enabled false
+	}
+}
+
 (security) {
 	# Basic rate limiting - 30 requests per minute per IP
 	header X-Rate-Limit "30/minute"
@@ -18,6 +25,14 @@
 	}
 }
 
+# Metrics endpoint - exposed on localhost only for vmagent scraping
+:9090 {
+	import telemetry
+	respond /metrics 200 {
+		content_type text/plain
+	}
+}
+
 *.mfilipe.eu {
 	tls {
 		dns gandi {env.GANDI_API_TOKEN}

caddy/Dockerfile

@@ -1,7 +1,8 @@
 FROM caddy:2-builder AS builder
 
 RUN xcaddy build \
-    --with github.com/caddy-dns/gandi
+    --with github.com/caddy-dns/gandi \
+    --with github.com/caddyserver/caddy/v2/modules/caddytelemetry
 
 FROM caddy:2
 

monitoring/vmagent/prometheus.yml

@@ -8,3 +8,7 @@ scrape_configs:
   - job_name: 'victoriametrics'
     static_configs:
       - targets: ['victoriametrics:8428']
+  - job_name: 'caddy'
+    static_configs:
+      - targets: ['localhost:9090']
+    metrics_path: /metrics