fix alerts and reduce Prometheus disk write rate

- linkwarden: add Reloader match annotation to DB secret so pods
  auto-restart on Vault credential rotation (was causing 100% 5xx)
- authentik: increase memory limits (server 1Gi→1.5Gi, worker 896Mi→1Gi)
  to prevent OOM kills
- prometheus: drop 113k high-cardinality series to reduce HDD write rate
  from ~8.8 to ~6.0 MB/s (31% reduction):
  - drop all traefik/apiserver/etcd histogram bucket metrics
  - drop goflow2_flow_process_nf_templates_total (9.3k series)
  - drop container_tasks_state and container_memory_failures_total
  - rewrite HighServiceLatency alert to use avg latency (_sum/_count)
  - update cluster_health dashboard to match
- raise KubeletRuntimeOperationsLatency threshold from 30s to 60s

stacks/authentik/modules/authentik/values.yaml

@@ -25,9 +25,9 @@ server:
   resources:
     requests:
       cpu: 100m
-      memory: 1Gi
+      memory: 1.5Gi
     limits:
-      memory: 1Gi
+      memory: 1.5Gi
   topologySpreadConstraints:
     - maxSkew: 1
       topologyKey: kubernetes.io/hostname
@@ -58,9 +58,9 @@ worker:
   resources:
     requests:
       cpu: 100m
-      memory: 896Mi
+      memory: 1Gi
     limits:
-      memory: 896Mi
+      memory: 1Gi
   topologySpreadConstraints:
     - maxSkew: 1
       topologyKey: kubernetes.io/hostname