Export and scrape metrics from all redis/valkey instances

No redis/valkey instance in the estate exports metrics today. Adds a
pinned redis_exporter (v1.89.0 via the artifactapi dockerhub remote)
next to every instance and two cluster-wide VMPodScrapes so the
observability VMAgent picks them all up.

- enables the valkey-operator exporter sidecar on the jellyfin
  ValkeyCluster, overriding the operator's bare-dockerhub default image
  with the artifactapi-proxied pin
- adds a metrics-exporter sidecar (:9121, port name metrics) to the
  artifactapi/authentik/litellm redis and gitea/netbox valkey
  Deployments, with the monitoring.unkin.net/redis-exporter opt-in pod
  label
- adds VMPodScrape redis-exporters selecting that label in any
  namespace, and VMPodScrape valkey-operator-clusters for
  operator-managed pods whose labels are fixed (the ValkeyCluster CR has
  no pod-label passthrough)

apps/base/observability/kustomization.yaml

@@ -9,3 +9,4 @@ resources:
   - gateway.yaml
   - httproute.yaml
   - vmpodscrape-cnpg.yaml
+  - vmpodscrape-redis.yaml

apps/base/observability/vmpodscrape-redis.yaml

@@ -0,0 +1,40 @@
+---
+# Scrape metrics (:9121) from every redis/valkey pod carrying a redis_exporter
+# sidecar in any namespace. Raw redis/valkey Deployments opt in via the
+# monitoring.unkin.net/redis-exporter pod label. Picked up by the observability
+# VMAgent (selectAllByDefault).
+apiVersion: operator.victoriametrics.com/v1beta1
+kind: VMPodScrape
+metadata:
+  name: redis-exporters
+  namespace: observability
+spec:
+  namespaceSelector:
+    any: true
+  selector:
+    matchLabels:
+      monitoring.unkin.net/redis-exporter: "true"
+  podMetricsEndpoints:
+    - port: metrics
+      path: /metrics
+---
+# valkey-operator-managed ValkeyCluster pods (e.g. jellyfin-valkey) get fixed
+# operator labels only -- the ValkeyCluster CR has no pod-label passthrough, so
+# they cannot carry monitoring.unkin.net/redis-exporter and need their own
+# selector. The operator's exporter sidecar also listens on :9121 with a port
+# named `metrics`.
+apiVersion: operator.victoriametrics.com/v1beta1
+kind: VMPodScrape
+metadata:
+  name: valkey-operator-clusters
+  namespace: observability
+spec:
+  namespaceSelector:
+    any: true
+  selector:
+    matchLabels:
+      app.kubernetes.io/managed-by: valkey-operator
+      app.kubernetes.io/component: valkey-node
+  podMetricsEndpoints:
+    - port: metrics
+      path: /metrics