Update kube-prometheus-stack values.yaml to clarify Loki datasource configuration and enhance observability documentation in CLUSTER-BUILD.md. Include deployment instructions for Loki and Fluent Bit, and mark tasks related to Grafana integration as completed.

clusters/noble/apps/loki/namespace.yaml

@@ -0,0 +1,9 @@
+# Loki (SingleBinary + filesystem on Longhorn) — apply before Helm.
+apiVersion: v1
+kind: Namespace
+metadata:
+  name: loki
+  labels:
+    pod-security.kubernetes.io/enforce: baseline
+    pod-security.kubernetes.io/audit: baseline
+    pod-security.kubernetes.io/warn: baseline