feat(authentik): adopt admin-services-restriction policy; admit kubernetes-* groups to k8s dashboard

Namespace-owners (e.g. gheorghe) were blocked at forward-auth — k8s.viktorbarzin.me
was Home-Server-Admins-only. Carve-out: the dashboard host now also admits
kubernetes-admins/power-users/namespace-owners so they can reach the login page;
per-namespace access is still enforced by the pasted SA token (dashboard-sa.tf).
All other admin-only hosts unchanged. Policy adopted from UI into TF via import.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

stacks/authentik/admin-services-restriction.tf

@@ -0,0 +1,64 @@
+# Catch-all forward-auth restriction: gate the admin-only hostnames to the
+# "Home Server Admins" group. Bound to the "Domain wide catch all" application
+# (binding stays UI-managed; only the expression is adopted here).
+#
+# Adopted into Terraform 2026-06-04 to add a carve-out: the Kubernetes Dashboard
+# (k8s.viktorbarzin.me) ALSO admits the kubernetes-* RBAC groups, so
+# namespace-owners (e.g. gheorghe) can reach the dashboard login page. The
+# dashboard itself enforces per-namespace access via the pasted ServiceAccount
+# token (stacks/rbac/modules/rbac/dashboard-sa.tf) — this policy only controls
+# who reaches the page. All other admin-only hosts remain Home-Server-Admins-only.
+import {
+  to = authentik_policy_expression.admin_services_restriction
+  id = "07a11b85-8f37-4844-aebb-ac9c112ec87c"
+}
+
+resource "authentik_policy_expression" "admin_services_restriction" {
+  name = "admin-services-restriction"
+  expression = trimspace(<<-EOT
+    ADMIN_ONLY_HOSTS = {
+        "terminal.viktorbarzin.me",
+        "frigate.viktorbarzin.me",
+        "netbox.viktorbarzin.me",
+        "trading.viktorbarzin.me",
+        "speedtest.viktorbarzin.me",
+        "meshcentral.viktorbarzin.me",
+        "k8s.viktorbarzin.me",
+        "dashy.viktorbarzin.me",
+        "prowlarr.viktorbarzin.me",
+        "qbittorrent.viktorbarzin.me",
+        "listenarr.viktorbarzin.me",
+        "shlink.viktorbarzin.me",
+        "openclaw.viktorbarzin.me",
+        "openlobster.viktorbarzin.me",
+        "wealthfolio.viktorbarzin.me",
+    }
+
+    ADMIN_GROUP = "Home Server Admins"
+
+    # The K8s Dashboard additionally admits the Kubernetes RBAC groups. Access
+    # to the page is not the security boundary — the pasted ServiceAccount token
+    # is (per-namespace admin + cluster read-only). See dashboard-sa.tf.
+    K8S_DASHBOARD_HOST = "k8s.viktorbarzin.me"
+    K8S_DASHBOARD_GROUPS = [
+        "Home Server Admins",
+        "kubernetes-admins",
+        "kubernetes-power-users",
+        "kubernetes-namespace-owners",
+    ]
+
+    host = request.context.get("host", "")
+
+    # Not an admin-only host: allow any authenticated user.
+    if host not in ADMIN_ONLY_HOSTS:
+        return True
+
+    # K8s Dashboard: allow admins OR any Kubernetes RBAC group.
+    if host == K8S_DASHBOARD_HOST:
+        return any(ak_is_group_member(request.user, name=g) for g in K8S_DASHBOARD_GROUPS)
+
+    # Every other admin-only host: Home Server Admins only.
+    return ak_is_group_member(request.user, name=ADMIN_GROUP)
+  EOT
+  )
+}