PERF(prometheus): optimize prometheus memory usage

- Increase scrapeInterval: 30s → 60s
- Increase evaluationInterval: 30s → 60s
- Reduce retention: 7d → 3d
- Add memory limit: 1Gi (prevent unlimited growth)
- Increase memory request: 256Mi → 512Mi (reflect actual usage)

prometheus/helm-values.yaml

@@ -37,23 +37,25 @@ prometheus:
   enabled: true
   
   prometheusSpec:
-    scrapeInterval: 30s
-    evaluationInterval: 30s
-    retention: 7d
+    scrapeInterval: 60s       # 30s → 60s (메모리 절감)
+    evaluationInterval: 60s   # 30s → 60s
+    retention: 3d             # 7d → 3d (메모리 절감)
 
     storageSpec:
       volumeClaimTemplate:
         spec:
-          storageClassName: longhorn  # Migrated from local-path to Longhorn (replica=3)
+          storageClassName: longhorn
           accessModes: ["ReadWriteOnce"]
           resources:
             requests:
               storage: 5Gi
 
     resources:
+      limits:
+        memory: 1Gi           # limit 추가 (무제한 증가 방지)
       requests:
-        cpu: 200m  # Increased from 50m (actual usage: 188m)
-        memory: 256Mi
+        cpu: 200m
+        memory: 512Mi         # 256Mi → 512Mi (실제 사용량 반영)
     
     # ServiceMonitor 자동 발견 - 모든 ServiceMonitor 선택
     serviceMonitorSelectorNilUsesHelmValues: false