feat(runner): add docker CLI to act_runner image for host-exec labels

qa/self-hosted labels run jobs directly in the runner container (Alpine),
which lacked a docker client despite the mounted host socket.

runner/Dockerfile

@@ -0,0 +1,2 @@
+FROM gitea/act_runner:latest
+RUN apk add --no-cache docker-cli docker-cli-compose

runner/compose.yml

@@ -1,6 +1,6 @@
 services:
   runner:
-    image: gitea/act_runner:latest
+    build: .
     container_name: gitea-runner
     restart: unless-stopped
     environment:

runner/config.yaml

@@ -64,6 +64,8 @@ runner:
     - "ubuntu-latest:docker://docker.gitea.com/runner-images:ubuntu-latest"
     - "ubuntu-24.04:docker://docker.gitea.com/runner-images:ubuntu-24.04"
     - "ubuntu-22.04:docker://docker.gitea.com/runner-images:ubuntu-22.04"
+    - "qa"
+    - "self-hosted"
 
 cache:
   # Enable cache server to use actions/cache.