docs(collection): document all roles and fix metadata drift

Replace ansible-galaxy init placeholders across the collection and
correct documentation that drifted from the code, after a multi-agent
review of every role README against its defaults, tasks and templates.

Collection level:
- README: role table for all 16 roles, requirements and role-ordering
- galaxy.yml: declare community.docker and community.general deps,
  real description/tags/urls; normalize license to MIT-0
- meta/runtime.yml: requires_ansible '>=2.15.0'
- plugins/README: document the homarr_layout filter and
  garage_credentials lookup instead of scaffold boilerplate

Per-role meta/main.yml and README for the placeholder roles
(389ds, authentik, authentik_outpost_ldap, base, collabora, drawio,
garage, homarr, httpbin, keycloak, nextcloud, opencloud, traefik).

Correctness fixes found during review:
- keycloak: wrong domain default, drop invented keycloak_cert_resolver,
  document the provisioning feature
- garage: root_domain is .s3.<first-entry>, not the bare domain
- opnform: jwt/front_api secrets use `openssl rand -hex 32`; align the
  validation fail_msg in tasks/main.yml accordingly
- send: S3 example references garage_s3_domains[0] (was singular)
- opencloud: document required opencloud_wopi_domain

License normalized to MIT-0 across galaxy.yml, role meta and READMEs to
match the SPDX headers.

roles/traefik/meta/argument_specs.yml

@@ -109,10 +109,11 @@ argument_specs:
         type: bool
         default: false
         description:
-          - Disable lego's propagation check against the zone's authoritative
-            nameservers (sets C(LEGO_DISABLE_CNAME_SUPPORT=) plus the
-            authoritative-NS-check skip). Use when the SOA-listed NS hostname
-            resolves to an address the proxy host cannot reach.
+          - "Sets C(propagation.disableANSChecks) to true on the ACME resolver
+            in the static config, disabling lego's propagation check against
+            the zone's authoritative nameservers. Use when the SOA-listed NS
+            hostname resolves to an address the proxy host cannot reach; lego
+            still polls via the configured C(resolvers) list."
 
       traefik_selfsigned_cert_dir:
         type: path