feat(poimen): consolidate into single multi-source ArgoCD app

- Merge poimen-workflows + poimen-memory + db + frontend into one app
- Delete duplicate apps: poimen-workflows, poimen-memory-app (kubectl done)
- Delete poimen-memory ArgoCD app file (replaced by multi-source source 2)
- Delete poimen-memory-database (replaced by source 3 → k8s/infra/poimen/)
- Move memory-db CNPG cluster to k8s/infra/poimen/ (isolated from other tenants)
- Remove memory-db from k8s/infra/databases/kustomization.yaml
- Add frontend manifests (Deployment, Service, Ingress) to k8s/apps/poimen/
- Add frontend NetworkPolicy: egress to api-gw (api:8080), memory (poimen:8080),
  Gotify (notifications:80), Authentik (iam:9000/9443), DNS (kube-system:53)
- Sync-wave -1 on CNPG cluster ensures DB ready before app pods (wave 0)
- Image updater: workflows + memory + frontend tracked in one annotation block
- poimen-toolkit stays separate (CRD management, independent rollback)

k8s/infra/databases/kustomization.yaml

@@ -8,5 +8,4 @@ resources:
   - namespaces.yaml
   - authentik-db.yaml
   - temporal-db.yaml
-  - memory-db.yaml
   - paperless-db.yaml

k8s/infra/poimen/kustomization.yaml

@@ -0,0 +1,8 @@
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+# Poimen infrastructure — CNPG Postgres for memory service.
+# Part of the `poimen` ArgoCD Application (multi-source, source 3).
+# Sync-wave -1 ensures the DB cluster is healthy before application
+# deployments (wave 0) are applied.
+resources:
+  - memory-db.yaml

k8s/infra/poimen/memory-db.yaml

@@ -0,0 +1,37 @@
+# Dedicated CNPG Postgres for Poimen Memory (GitOps, wave 2).
+# Uses default longhorn storage class (3 replicas, dataLocality disabled).
+# CNPG generates secret `memory-db-app` + service `memory-db-rw` in ns poimen.
+apiVersion: postgresql.cnpg.io/v1
+kind: Cluster
+metadata:
+  name: memory-db
+  namespace: poimen
+  annotations:
+    argocd.argoproj.io/sync-wave: "-1"
+    argocd.argoproj.io/sync-options: SkipDryRunOnMissingResource=true
+spec:
+  instances: 3
+  imageName: ghcr.io/cloudnative-pg/postgresql:16.2
+  bootstrap:
+    initdb:
+      database: memory
+      owner: app
+      encoding: UTF8
+      localeCollate: C
+      localeCType: C
+      postInitApplicationSQL:
+        - "CREATE EXTENSION vector;"
+  enableSuperuserAccess: false
+  resources:
+    requests: { memory: "512Mi", cpu: "250m" }
+    limits: { memory: "2Gi", cpu: "1" }
+  storage:
+    size: 20Gi
+    storageClass: longhorn
+  affinity:
+    podAntiAffinityType: preferred
+    topologyKey: kubernetes.io/hostname
+    tolerations:
+      - key: node-role.kubernetes.io/control-plane
+        operator: Exists
+        effect: NoSchedule