feat: domain list refactor + demo-gymburgdorf fixes

- Refactor: collapse `*_domain` + `*_extra_domains` into a single
  `*_domains` list across authentik, collabora, garage and nextcloud
  roles. First entry is the canonical FQDN (used for OVERWRITEHOST,
  BASE_URL, notify_push setup and garage root_domain).
- Authentik blueprint: guard the OAuth sources block so an empty
  `authentik_login_sources` no longer renders an invalid YAML key.
- Nextcloud: introduce `nextcloud_collabora_public_domain` and set
  Collabora's `public_wopi_url` separately from the server-to-server
  `wopi_url` so browsers can reach Collabora via the public name while
  Nextcloud still talks to it on the internal one.
- Nextcloud: URL-encode the postgres user/password in DATABASE_URL.

roles/collabora/defaults/main.yml

@@ -12,7 +12,11 @@ collabora_docker_compose_dir: "{{ docker_compose_base_dir }}/{{ collabora_servic
 collabora_docker_volume_dir: "{{ docker_volume_base_dir }}/{{ collabora_service_name }}"
 
 # Service configuration
-collabora_domain: "office.local.test"
+# FQDNs the collabora router accepts. The first entry is the canonical
+# domain; further entries cover internal *.int.* names used for
+# server-to-server WOPI discovery.
+collabora_domains:
+  - "office.local.test"
 collabora_image: "collabora/code:latest"
 collabora_port: 9980
 collabora_extra_hosts: []