feat: support multiple Gitea instances for actions runner

The gitea-actions role now uses a `gitea_runners` list instead of a
single `gitea_instance_url`. Each instance gets its own config, systemd
service, working directory, and cache. Migrates from the old single
`act_runner.service` to per-instance `act_runner-{name}.service`.

Adds git.skudak.com alongside git.debyl.io as runner targets.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ansible/roles/gitea-actions/tasks/systemd.yml

@@ -1,17 +1,37 @@
 ---
-- name: deploy act_runner systemd service
-  become: true
-  ansible.builtin.template:
-    src: act_runner.service.j2
-    dest: /etc/systemd/system/act_runner.service
-    mode: "0644"
-  notify: restart act_runner
-  tags: gitea-actions
-
-- name: enable act_runner service
+- name: stop and disable legacy act_runner service
   become: true
   ansible.builtin.systemd:
     name: act_runner
+    state: stopped
+    enabled: false
+  failed_when: false
+  tags: gitea-actions
+
+- name: remove legacy act_runner service file
+  become: true
+  ansible.builtin.file:
+    path: /etc/systemd/system/act_runner.service
+    state: absent
+  tags: gitea-actions
+
+- name: deploy per-runner systemd service
+  become: true
+  ansible.builtin.template:
+    src: act_runner.service.j2
+    dest: "/etc/systemd/system/act_runner-{{ item.name }}.service"
+    mode: "0644"
+  vars:
+    runner_name: "{{ item.name }}"
+  loop: "{{ gitea_runners }}"
+  notify: restart act_runner services
+  tags: gitea-actions
+
+- name: enable per-runner services
+  become: true
+  ansible.builtin.systemd:
+    name: "act_runner-{{ item.name }}"
     daemon_reload: true
     enabled: true
+  loop: "{{ gitea_runners }}"
   tags: gitea-actions