FEAT(loki): configure storage and HA

- Rename extraVolume to avoid duplicate name
- Add emptyDir for /var/loki cache
- Migrate to shared storage with MinIO
- Configure HA with 2 replicas
- Revert to single replica for Single Binary mode

grafana/helm-values.yaml

@@ -3,6 +3,18 @@
 
 fullnameOverride: grafana
 
+replicas: 2
+
+affinity:
+  podAntiAffinity:
+    preferredDuringSchedulingIgnoredDuringExecution:
+    - weight: 100
+      podAffinityTerm:
+        labelSelector:
+          matchLabels:
+            app.kubernetes.io/name: grafana
+        topologyKey: kubernetes.io/hostname
+
 admin:
   user: bluemayne
   # Password is managed via SealedSecret: grafana-admin-password