CHORE(resources): set memory limits equal to memory requests

Align memory limits with memory requests for guaranteed QoS class.
- prometheus, thanos (query, storegateway, compactor)
- alertmanager, tempo, goldilocks (dashboard, controller)
- node-exporter, opentelemetry-collector, vpa, kube-state-metrics

prometheus/helm-values.yaml

@@ -86,7 +86,7 @@ prometheus:
         cpu: 50m
         memory: 512Mi
       limits:
-        memory: 768Mi
+        memory: 512Mi
     
     # ServiceMonitor 자동 발견 - 모든 ServiceMonitor 선택
     serviceMonitorSelectorNilUsesHelmValues: false