GRM-14: feat: add systemd template units and multi-instance Ansible support

- Add instance-scoped base data/config directories in defaults
- Create gitea-runner@.service.j2 template supporting Docker and binary modes
- Refactor service.yml to install systemd template unit instances
- Remove direct container lifecycle from docker_mode.yml (delegate to systemd)
- Add deregister.yml for runner deregistration on disable/remove
- Create lifecycle playbooks: start, stop, enable, disable, status, remove
- Update handlers, integration_test, docker_update, binary_update for template units

ansible/roles/gitea-runner/tasks/docker_mode.yml

@@ -44,26 +44,5 @@
   changed_when: "'already exists' not in register_output.stdout | default('')"
   timeout: 60
 
-- name: Check if gitea_runner container exists
-  ansible.builtin.command: docker inspect -f '{{ '{{' }} .State.Running {{ '}}' }}' gitea-runner-{{ runner_name }}
-  register: container_check
-  changed_when: false
-  failed_when: container_check.rc != 0 and 'no such object' not in container_check.stderr
-
-- name: Run gitea_runner daemon container
-  ansible.builtin.command: >
-    docker run -d
-    --name gitea-runner-{{ runner_name }}
-    --restart unless-stopped
-    --entrypoint /usr/local/bin/gitea-runner
-    -v /var/run/docker.sock:/var/run/docker.sock
-    -v {{ gitea_runner_data_dir }}:/data
-    -w /data
-    {{ gitea_runner_docker_image }}:{{ gitea_runner_version | regex_replace('^v', '') }}
-    daemon
-    --config /data/config.yaml
-  when:
-    - container_check.rc != 0
-    - not skip_runner_registration
-  register: docker_run
-  changed_when: docker_run.rc == 0
+- name: Include service setup
+  ansible.builtin.include_tasks: service.yml