Send the admin login straight to Dex

A public custom script submits the OIDC form on /admin/login and CSS
hides the password form. /admin/login?local=1 (or a failed password
attempt) shows it for break-glass use; a 15s guard prevents loops.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

templates/configure.sql.j2

@@ -52,6 +52,7 @@
   }],
   'appearance.public.custom_css': lookup('ansible.builtin.file', role_path ~ '/files/public.css'),
   'appearance.admin.custom_css': lookup('ansible.builtin.file', role_path ~ '/files/admin.css'),
+  'appearance.public.custom_js': lookup('ansible.builtin.file', role_path ~ '/files/public.js'),
 } | combine(listmonk_settings_extra) -%}
 \set ON_ERROR_STOP on
 BEGIN;