Use the docker compose plugin instead of a standalone binary

- install docker-compose-plugin from the docker repo and remove /usr/local/bin/docker-compose (pinned 2.29.0)
- remove the legacy download_docker_com_linux_debian.list (no signed-by), which made apt refuse the docker sources

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

tasks/main.yml

@@ -24,6 +24,13 @@
     dest: /etc/apt/keyrings/docker.asc
     mode: '0644'
 
+# older versions of this role created this file without signed-by; apt
+# refuses two docker sources with different Signed-By values
+- name: remove legacy docker repository file
+  file:
+    path: /etc/apt/sources.list.d/download_docker_com_linux_debian.list
+    state: absent
+
 # write the whole file so repo lines of older releases do not linger
 - name: Add Docker repository
   copy:
@@ -45,11 +52,11 @@
     pkg:
       - docker-ce
       - docker-ce-cli
+      - docker-compose-plugin
       - python3-docker
 
-# Docker Compose
-- name: download latest docker
-  get_url:
-    url: "https://github.com/docker/compose/releases/download/v{{ docker_compose_version }}/docker-compose-linux-{{ ansible_architecture }}"
-    dest: /usr/local/bin/docker-compose
-    mode: 0755
+# Docker Compose: use the "docker compose" plugin from the docker repo
+- name: remove standalone docker-compose binary
+  file:
+    path: /usr/local/bin/docker-compose
+    state: absent