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/drawio/meta/main.yml

@@ -1,35 +1,26 @@
 #SPDX-License-Identifier: MIT-0
 galaxy_info:
-  author: your name
-  description: your role description
-  company: your company (optional)
+  author: digitalboard
+  description: Deploy the draw.io diagram editor via Docker Compose behind Traefik, with optional authentik ForwardAuth
+  company: Digitalboard
+  license: MIT-0
 
-  # If the issue tracker for your role is not on github, uncomment the
-  # next line and provide a value
-  # issue_tracker_url: http://example.com/issue/tracker
+  min_ansible_version: "2.14"
 
-  # Choose a valid license ID from https://spdx.org - some suggested licenses:
-  # - BSD-3-Clause (default)
-  # - MIT
-  # - GPL-2.0-or-later
-  # - GPL-3.0-only
-  # - Apache-2.0
-  # - CC-BY-4.0
-  license: license (GPL-2.0-or-later, MIT, etc)
+  platforms:
+    - name: Debian
+      versions:
+        - bookworm
+    - name: Ubuntu
+      versions:
+        - jammy
+        - noble
 
-  min_ansible_version: 2.2
-
-  # If this a Container Enabled role, provide the minimum Ansible Container version.
-  # min_ansible_container_version:
-
-  galaxy_tags: []
-    # List tags for your role here, one per line. A tag is a keyword that describes
-    # and categorizes the role. Users find roles by searching for tags. Be sure to
-    # remove the '[]' above, if you add tags to this list.
-    #
-    # NOTE: A tag is limited to a single word comprised of alphanumeric characters.
-    #       Maximum 20 tags per role.
+  galaxy_tags:
+    - drawio
+    - diagrams
+    - docker
+    - traefik
+    - digitalboard
 
 dependencies: []
-  # List your role dependencies here, one per line. Be sure to remove the '[]' above,
-  # if you add dependencies to this list.