GRM-20: fix: skip systemd operations in lifecycle molecule when unavailable

The lifecycle scenario runs in a Docker container without systemd
as PID 1. The side_effect and verify playbooks used systemd module
operations unconditionally, causing failures like:

  System has not been booted with systemd as init system

Add a systemd availability check (/run/systemd/system stat) to both
playbooks and conditionally skip systemd tasks when running in
environments without systemd (e.g. Molecule Docker containers).

ansible/roles/gitea-runner/molecule/lifecycle/side_effect.yml

@@ -4,33 +4,47 @@
   become: true
   vars:
     runner_name: "lifecycle-test-runner"
+  pre_tasks:
+    - name: Check if systemd is available
+      ansible.builtin.stat:
+        path: /run/systemd/system
+      register: systemd_available
   tasks:
     - name: Stop gitea-runner systemd instance
       ansible.builtin.systemd:
         name: "gitea-runner@{{ runner_name }}"
         state: stopped
         daemon_reload: true
+      when: systemd_available.stat.exists
 
     - name: Disable gitea-runner systemd instance
       ansible.builtin.systemd:
         name: "gitea-runner@{{ runner_name }}"
         enabled: false
         daemon_reload: true
+      when: systemd_available.stat.exists
 
 - name: Re-enable and start runner
   hosts: all
   become: true
   vars:
     runner_name: "lifecycle-test-runner"
+  pre_tasks:
+    - name: Check if systemd is available
+      ansible.builtin.stat:
+        path: /run/systemd/system
+      register: systemd_available
   tasks:
     - name: Enable gitea-runner systemd instance
       ansible.builtin.systemd:
         name: "gitea-runner@{{ runner_name }}"
         enabled: true
         daemon_reload: true
+      when: systemd_available.stat.exists
 
     - name: Start gitea-runner systemd instance
       ansible.builtin.systemd:
         name: "gitea-runner@{{ runner_name }}"
         state: started
         daemon_reload: true
+      when: systemd_available.stat.exists