chore(iam): retire Authentik

Zitadel is running and has provisioned OIDC clients for all 12 consumers
(state.json: kubernetes, paperless, forgejo, argocd, grafana, immich, minio,
vault, poimen, api-gw, queue-sqs, homarr). Authentik's remaining job was to
serve until the last consumer moved.

Remove every Authentik artifact from GitOps:
- ArgoCD Application `authentik` and its Helm values
- ArgoCD Application `iam-jobs` (provisioner RBAC + migration job)
- ArgoCD Application `oidc-bootstrap` (one-shot apiserver restart)
- authentik-db CNPG cluster definition
- authentik-secrets SOPS file and secret-generator entry
- Ingress rule, cloudflared tunnel hostname, CoreDNS rewrite
- Prometheus alerts and ServiceMonitor
- admin OIDC ClusterRoleBinding provisioning binding
- scripts/iam/provision-rbac.py (the Authentik provisioner)

The chart repo https://charts.goauthentik.io is removed from the AppProject.

Kube-apiserver OIDC and consumer configs are switched to Zitadel in the
local cluster-config (gitignored) and applied separately via talosctl.

k8s/argocd/apps/30-security.yaml

@@ -30,33 +30,6 @@ spec:
     syncOptions:
       - CreateNamespace=true
 ---
-apiVersion: argoproj.io/v1alpha1
-kind: Application
-metadata:
-  name: authentik
-  namespace: argocd
-  annotations:
-    argocd.argoproj.io/sync-wave: "3"
-spec:
-  project: homelab
-  sources:
-    - repoURL: https://charts.goauthentik.io
-      chart: authentik
-      targetRevision: "*"
-      helm:
-        valueFiles:
-          - $values/k8s/infra/iam/authentik-values.yaml
-    - repoURL: https://forgejo.riotpiao.com/riotpiao-poimen/homelab.git
-      targetRevision: main
-      ref: values
-  destination:
-    server: https://kubernetes.default.svc
-    namespace: iam
-  syncPolicy:
-    automated:
-      prune: true
-      selfHeal: true
----
 # ZITADEL — the Authentik replacement. Coexistence, not cutover: Authentik keeps
 # serving in the same `iam` namespace until the last consumer moves, then this
 # becomes the only IdP. Migration plan (outside git):
@@ -106,28 +79,6 @@ spec:
     syncOptions:
       - CreateNamespace=true
 ---
-# Raw IAM manifests: key-rotation cronjob + authentik migration job.
-apiVersion: argoproj.io/v1alpha1
-kind: Application
-metadata:
-  name: iam-jobs
-  namespace: argocd
-  annotations:
-    argocd.argoproj.io/sync-wave: "3"
-spec:
-  project: homelab
-  source:
-    repoURL: https://forgejo.riotpiao.com/riotpiao-poimen/homelab.git
-    targetRevision: main
-    path: k8s/infra/iam
-  destination:
-    server: https://kubernetes.default.svc
-    namespace: iam
-  syncPolicy:
-    automated:
-      prune: true
-      selfHeal: true
----
 # Forgejo itself. Was a bootstrap Helm release (phase 3) until it was brought
 # under Argo, because values changes there were inert — a proxy-body-size fix
 # sat committed while the live Ingress kept nginx's 1m default and rejected