fix(monitoring): point probe-printweb at /health (Q-MR-90)

Root path requires API key auth — `/` returned 401 to the blackbox
probe, firing PrintWebDown despite `/health` reporting Healthy.
Pattern: feedback_k8s_probes_behind_auth_middleware.

Mirrors FlowerCore.Notes scripts/monitoring/prometheus.yml.

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

apps/monitoring/noc-monitoring.yaml

@@ -280,13 +280,14 @@ data:
               printer_model: "NuPrint 210"
 
       # Print.Web health (Blazor app on edge2:5200)
+      # Target `/health` (anonymous) — root path requires API key auth and returns 401.
       - job_name: "probe-printweb"
         metrics_path: /probe
         params:
           module: [http_2xx]
         scrape_interval: 30s
         static_configs:
-          - targets: ["http://10.0.57.16:5200/"]
+          - targets: ["http://10.0.57.16:5200/health"]
             labels:
               instance: "print-web"
               service: "print-web"