Fix observability issues and refactor metrics stack to ArgoCD

- Resolved "connection refused" on startup probe by explicitly mapping management.server.port in application.yaml.
- Adjusted startupProbe to a 70s window (10s delay + 12 * 5s) to accommodate application initialization.
- Externalized VictoriaMetrics stack (Operator, Single, Agent, Alert) into separate ArgoCD Application manifests.
- Removed bundled VictoriaMetrics templates from the MovieNight Helm chart.
- Configured vmagent with Kubernetes pod-based service discovery for metrics scraping.
- Ensured consistency between Helm values and externalized observability components.

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

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

@@ -62,10 +62,6 @@ 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 }}