fix(loki): zero SimpleScalable replicas and disable unused components

Loki chart v6.x ships with non-zero defaults for read/write/backend
even when deploymentMode: SingleBinary is set, which trips the chart's
validate.yaml ("more than zero replicas configured for both ..."
error). Explicitly set them to 0.

Also disable chunksCache / resultsCache (memcached), gateway,
lokiCanary, and test hooks — unnecessary for a single-node ARM64
deployment and they add memory pressure.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: soohyunme

infrastructure/base/monitoring/loki/values.yaml

@@ -15,6 +15,27 @@ singleBinary:
     size: 50Gi
     storageClass: local-path
 
+# Loki chart v6.x: explicitly zero SimpleScalable targets so the
+# chart's validate.yaml accepts SingleBinary-only deployment.
+read:
+  replicas: 0
+write:
+  replicas: 0
+backend:
+  replicas: 0
+
+# Disable auxiliary components not needed on single-node ARM64
+chunksCache:
+  enabled: false
+resultsCache:
+  enabled: false
+gateway:
+  enabled: false
+lokiCanary:
+  enabled: false
+test:
+  enabled: false
+
 loki:
   auth_enabled: false