infra: redirect alloy-k8s devpi probe to public URL

The blackbox probe was pointing at the in-cluster devpi service,
which no longer exists. Probe https://pypi.ops.eblu.me/+api instead;
the cluster reaches it via Tailscale + Caddy on indri.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

argocd/manifests/alloy-k8s/config.alloy

@@ -159,8 +159,10 @@ prometheus.exporter.blackbox "services" {
   }
 
   target {
+    // devpi runs natively on indri (LaunchAgent), not in-cluster.
+    // We probe through Caddy (https://pypi.ops.eblu.me) which the cluster can reach via Tailscale.
     name    = "devpi"
-    address = "http://devpi.devpi.svc.cluster.local:3141/+api"
+    address = "https://pypi.ops.eblu.me/+api"
     module  = "http_2xx"
   }