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/templates/config.yaml.j2

@@ -2,7 +2,7 @@ log:
   level: info
 
 runner:
-  file: {{ act_runner_work_dir }}/.runner
+  file: {{ act_runner_work_dir }}/{{ runner_name }}/.runner
   capacity: 1
   timeout: 3h
   insecure: false
@@ -15,7 +15,7 @@ runner:
 
 cache:
   enabled: true
-  dir: {{ act_runner_work_dir }}/cache
+  dir: {{ act_runner_work_dir }}/{{ runner_name }}/cache
 
 container:
   network: host
@@ -27,4 +27,4 @@ container:
   force_pull: false
 
 host:
-  workdir_parent: {{ act_runner_work_dir }}/workdir
+  workdir_parent: {{ act_runner_work_dir }}/{{ runner_name }}/workdir