refactor(poimen): move frontend k8s manifests to poimen-frontend repo

- Remove Deployment/Service/NetworkPolicy from homelab (wrong place)
- Add k8s/apps/poimen-frontend/ with ingress only (edge concern, same as api-gw)
- Update 70-poimen.yaml: source 4 → poimen-frontend.git k8s/
                          source 5 → homelab k8s/apps/poimen-frontend/ (ingress)

k8s/apps/poimen-frontend/kustomization.yaml

@@ -0,0 +1,8 @@
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+# Edge Ingress for poimen.riotpiao.com.
+# Same pattern as k8s/apps/api/ (api-gw ingress).
+# App manifests (Deployment, Service, NetworkPolicy) live in
+# riotpiao-poimen/poimen-frontend.git k8s/ — each repo owns its own k8s.
+resources:
+  - ingress.yaml