authentik: serve LDAP via an outpost behind the internal gateway

Adds the LDAP outpost deployment and routes ports 389 and 636 on
gateway-internal to it. 636 is a TLS listener in Terminate mode so
cert-manager renews the LDAPS certificate automatically, and both
listeners forward to the outpost's plaintext 3389.

allowedRoutes.kinds is set explicitly on both listeners: a TCP listener
permits no route kinds by default and a TLS listener defaults to
TLSRoute, so the TCPRoute would not attach otherwise.

applications/authentik/ldap/infisicalsecret.yaml

@@ -0,0 +1,24 @@
+apiVersion: secrets.infisical.com/v1alpha1
+kind: InfisicalSecret
+metadata:
+  name: authentik-ldap-secrets
+  namespace: infisical
+spec:
+  hostAPI: https://infisical.jsme.be
+  resyncInterval: 30
+  authentication:
+    kubernetesAuth:
+      identityId: "5458def7-7c63-40d2-95da-41c614d0933a"
+      serviceAccountRef:
+        name: infisical-auth
+        namespace: infisical
+      autoCreateServiceAccountToken: true
+      secretsScope:
+        projectSlug: "kubernetes"
+        envSlug: "prod"
+        secretsPath: "/authentik/authentik-ldap"
+        recursive: false
+  managedSecretReference:
+    secretName: authentik-ldap-secrets
+    secretNamespace: authentik
+    secretType: Opaque