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

thanos/helm-values.yaml

@@ -56,7 +56,7 @@ query:
       cpu: 15m
       memory: 128Mi
     limits:
-      memory: 256Mi
+      memory: 128Mi
 
 # =============================================================================
 # Query Frontend - Caching layer for Query (optional, disabled for small cluster)
@@ -84,7 +84,7 @@ storegateway:
       cpu: 15m
       memory: 128Mi
     limits:
-      memory: 512Mi
+      memory: 128Mi
 
   persistence:
     enabled: true
@@ -115,7 +115,7 @@ compactor:
       cpu: 15m
       memory: 128Mi
     limits:
-      memory: 512Mi
+      memory: 128Mi
 
   persistence:
     enabled: true