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/apps/poimen/kustomization.yaml

@@ -0,0 +1,12 @@
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+# Poimen frontend — Deployment, Service, Ingress for poimen.riotpiao.com.
+# Part of the `poimen` ArgoCD Application (multi-source, source 4).
+# All resources deploy into namespace `poimen` (same as workers and memory).
+# api-gw NetworkPolicy already allows ingress from namespace poimen.
+# Memory service is co-located — no additional NetworkPolicy needed.
+resources:
+  - frontend-deployment.yaml
+  - frontend-service.yaml
+  - frontend-ingress.yaml
+  - frontend-networkpolicy.yaml