feat: add ArgoCD Application and k8s manifests for frontend

- application.yaml: ArgoCD Application resource (manual sync for now,
  same pattern as nextgen-be)
- manifests/: namespace, deployment, service, ingress

application.yaml

@@ -0,0 +1,20 @@
+apiVersion: argoproj.io/v1alpha1
+kind: Application
+metadata:
+  name: nextgen-fe
+  namespace: argocd          # the namespace ArgoCD itself runs in — adjust if different
+  finalizers:
+    - resources-finalizer.argocd.argoproj.io
+spec:
+  project: default            # or your ArgoCD AppProject name, if you use one per subgroup
+  source:
+    repoURL: "ssh://git@gitea-ssh.gitea.svc.cluster.local:22/gitea_admin/nextgen-fe.git"
+    targetRevision: main
+    path: manifests
+  destination:
+    server: "https://138.199.131.114:6443"
+    namespace: nextgen-fe
+  syncPolicy: {}
+    # Left empty = manual sync. Switch to automated once nginx.conf/Ingress
+    # are confirmed working manually — see nextgen-be/application.yaml for
+    # the commented automated block to copy over.