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/secrets/authentik-secrets.enc.yaml

@@ -1,25 +0,0 @@
-apiVersion: ENC[AES256_GCM,data:Fc0=,iv:UFqMFeZTJZtFMoNeusjAoSI60U9StZS4IXw+n8JQCRM=,tag:uUvY4+jcjiSJHs0HDS3/7A==,type:str]
-kind: ENC[AES256_GCM,data:NUw86IEw,iv:gh4Vqn6uteYnYIFcXT/QVxRPKm+G+j2aIVuV71nZ4k4=,tag:nZA/x75Kx4+CoSx66BsvkQ==,type:str]
-metadata:
-    name: ENC[AES256_GCM,data:qex150pm0eGwYiiI05y9LUs=,iv:5Tk001T796c4HFikoh1ZVB6ierBfDqOUkFs5ilkr+V8=,tag:LiDAiCH7w6aRS41VKIlIKg==,type:str]
-    namespace: ENC[AES256_GCM,data:nI91,iv:c1hBWGMkVb+vg+MKNzty8CFfXxQabXEtT+EpiuQZNvo=,tag:BsGtJDbBadDdTa687+Sdag==,type:str]
-type: ENC[AES256_GCM,data:3rXawlSD,iv:FUtLK4KP7v/SBF08ZcU6siIO1qfjlJirf2x5PyzAjuA=,tag:mSIQ+Y43+wDfZGRbQ6a0Og==,type:str]
-stringData:
-    AUTHENTIK_SECRET_KEY: ENC[AES256_GCM,data:i5tVOWnN9a/cfhs6gckveRxUpiN7Ie227R/74kOIz6lQ5US2hkf03W5qSGCrzheL3DB0i8+d0iJYsApjn/wCiN7ndZZVFko3W5jDfVPybxc=,iv:djF1G9JHT5B7ziTokA/UuPpG+tG2LvFU4uMAR0x4M6o=,tag:vHOd7jLYkM8Evnr0QUVrCw==,type:str]
-    AUTHENTIK_BOOTSTRAP_PASSWORD: ENC[AES256_GCM,data:PjvYtH03CzQbTXEqt/Z18+u1zJdok7DLwDn51FUZXDA=,iv:pSwSm8hB0/Q8uOAcOZ1rTqq7BF782EglG19GGeghm1E=,tag:qGCQFWCrwsWBOiQ07ySMUQ==,type:str]
-    AUTHENTIK_BOOTSTRAP_TOKEN: ENC[AES256_GCM,data:1tnekGo0GIemJCMRenjN0yNeSiiMl/kky8ms84TsqBLaQ0lQzPxjq9qtgNJwoAsufxrznrkDVKjeOEHNYcA82A==,iv:NNFWSLMILoWccA9ihy1OArSS1X3OySB7PIHdXZdyzlg=,tag:t2w+KyReOXftTrU9pBQDnQ==,type:str]
-sops:
-    age:
-        - enc: |
-            -----BEGIN AGE ENCRYPTED FILE-----
-            YWdlLWVuY3J5cHRpb24ub3JnL3YxCi0+IFgyNTUxOSBSZGRKWm9PTkNSOENtREgx
-            M2V3Z0xxOXRhRGVRclo3SzBKRkc0VmtCY0NnClJPSGJRcUlzWmNFeTZ1bmorNEV4
-            U3l3TzVlMTlrWkJnQzBtUTJtcUwrM3MKLS0tIEJrMWZrbllYYUZKN1V4MVMzcXAv
-            eUtheHlNMHpsTEJXZ1FTMFVxbWloa0kKLRkE1Du+4gdOLerOl9y0mZw+8fqfECQY
-            uP64Q+9BSuPYNiTLZvYDzmdoy+KTS7i7C9rf+iU96R/crbQLamV9Ew==
-            -----END AGE ENCRYPTED FILE-----
-          recipient: age1e5fq3hwxy78psus2nfvmtmua36g0u3suk78ephw6246l974d2utsvn0hla
-    lastmodified: "2026-08-12T20:37:07Z"
-    mac: ENC[AES256_GCM,data:b3pDx340d1iZxsPPXzACckoLBrW+XjX1qlGrWEEI30j2Ao0hewTRZJyHbdI97A6b/hqzBN/4tjqqkdqm8goNhUQweMLTw86X6sALuE0aLS9wK53qjqih8fQwQBbgLDtjFXtW26h+smIm7aB5ZSDvU2le44HDXuWd83sWtCavNq0=,iv:ZMDsoKpygFJrYpXy2dA0IlxAi0jt24rxF72eUzgQs7k=,tag:WWE7G7+c9JK6fF1U9V8igg==,type:str]
-    unencrypted_suffix: _unencrypted
-    version: 3.13.2

k8s/argocd/secrets/secret-generator.yaml

@@ -9,7 +9,6 @@ metadata:
 files:
     - agent-pod-models.enc.yaml
     - agent-pod-ssh-key.enc.yaml
-    - authentik-secrets.enc.yaml
     - cloudflare-secrets.enc.yaml
     - cloudflared-credentials.enc.yaml
     - forgejo-registry-pat-api.enc.yaml