fc-signalcontrol: fix probe path /metrics/prometheus -> /health

The app exposes /health (Program.cs:91 maps a Healthy text response) but does
NOT expose /metrics/prometheus. K8s liveness/readiness probes against a 404
endpoint kept the pod in CrashLoopBackOff after PVC mount was added.

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

apps/fc-signalcontrol/fc-signalcontrol.yaml

@@ -65,13 +65,13 @@ spec:
               cpu: "500m"
           livenessProbe:
             httpGet:
-              path: /metrics/prometheus
+              path: /health
               port: 8080
             initialDelaySeconds: 10
             periodSeconds: 30
           readinessProbe:
             httpGet:
-              path: /metrics/prometheus
+              path: /health
               port: 8080
             initialDelaySeconds: 5
             periodSeconds: 10