feat(garage,authentik): console multi-domain + standalone proxy outpost

Two related additions for gating a cross-host service (garage WebUI on a
storage host) behind authentik without breaking on TLS or X-Forwarded-Host:

garage role:
- Add garage_webui_domains (list), mirroring garage_s3_domains. The
  console router now accepts every entry, so a DMZ reverseproxy can use a
  backend_host whose cert SAN matches an internal *.int.* name instead of
  connecting by IP (which fails acme cert verification). Defaults to the
  single garage_webui_domain so existing inventories are unaffected.

authentik_outpost_proxy role (new):
- Standalone proxy (ForwardAuth) outpost, modelled on authentik_outpost_ldap.
  Co-locate it with the protected service so the ForwardAuth subrequest
  reaches authentik over the local docker network. The embedded outpost
  only works for services on the authentik host: a cross-host subrequest
  routed through an extra reverse-proxy hop arrives with a polluted
  X-Forwarded-Host (port/comma-appended), which the outpost no longer
  matches against the provider's external_host (404).

roles/garage/defaults/main.yml

@@ -20,7 +20,15 @@ garage_image: "dxflrs/garage:v2.1.0"
 garage_s3_domains:
   - "storage.local.test"
 garage_web_domain: "web.storage.local.test"
+# Canonical WebUI console hostname (first entry of garage_webui_domains).
 garage_webui_domain: "console.storage.local.test"
+# FQDNs the WebUI console router accepts. The first entry is the canonical
+# public domain; further entries cover internal *.int.* names so a DMZ
+# reverseproxy can use a backend_host whose cert SAN matches (same pattern
+# as garage_s3_domains). Defaults to just the canonical domain so existing
+# inventories that only set garage_webui_domain keep working unchanged.
+garage_webui_domains:
+  - "{{ garage_webui_domain }}"
 
 # Garage WebUI configuration
 garage_webui_enabled: true