fix(helm): CronJob curls the Service port, not the container port

Service listens on port 80 (target: container 8080). The CronJob was
curling :8080 directly, which isn't exposed by the Service — every tick
timed out after ~135s with "Could not connect to server".

Switch to {{ .Values.service.port }} so the template always tracks the
actual Service port.

backend/deploy/helm/templates/discovery-cron.yaml

@@ -37,7 +37,7 @@ spec:
                   curl -fsS --retry 2 --retry-delay 10 \
                     -X POST \
                     -H "Authorization: Bearer $DISCOVERY_TOKEN" \
-                    "http://{{ include "marktvogt-backend.fullname" . }}:8080/api/v1/admin/discovery/tick"
+                    "http://{{ include "marktvogt-backend.fullname" . }}:{{ .Values.service.port }}/api/v1/admin/discovery/tick"
               env:
                 - name: DISCOVERY_TOKEN
                   valueFrom: