Fix observability and startup probe issues

- Explicitly configure management port 8081 in application.yaml to resolve connection refused errors.
- Adjust startupProbe failure threshold and initial delay in Helm chart to allow for a one-minute startup time.
- Update vmagent to use Kubernetes pod discovery for metrics scraping, adding necessary RBAC Role and RoleBinding.
- Introduce 'json-logging' Spring profile for structured console logging in Kubernetes.
- Add support for VictoriaMetrics Operator CRDs (VMSingle, VMAgent, VMPodScrape) to leverage the existing operator in the cluster.
- Review and refine observability templates for better integration with the VictoriaMetrics stack.

Co-authored-by: devitq <118541411+devitq@users.noreply.github.com>

deploy/helm/movienight/templates/backend/deployment.yaml

@@ -62,6 +62,10 @@ spec:
 {{- if .Values.observability.enabled }}
             - name: MANAGEMENT_METRICS_TAGS_APPLICATION
               value: {{ .Values.observability.metrics.applicationTag | quote }}
+{{- if .Values.observability.jsonLogging }}
+            - name: SPRING_PROFILES_ACTIVE
+              value: json-logging
+{{- end }}
 {{- end }}
 {{- if $postgresEnv }}
 {{- $postgresEnv | nindent 12 }}