fix act-runner: mount config.yaml with container.network=ci

act_runner needs a config file (not env var) to set the Docker
network for job containers. Without this, job containers can't
resolve 'gitea' hostname during checkout.

act-runner/config.yaml

@@ -0,0 +1,13 @@
+log:
+  level: info
+
+runner:
+  file: /data/.runner
+  capacity: 2
+  timeout: 3h
+
+container:
+  network: "ci"
+  privileged: true
+  options: ""
+  workdir_parent: ""

compose.yml

@@ -227,10 +227,11 @@ services:
       - GITEA_RUNNER_REGISTRATION_TOKEN=${ACT_RUNNER_TOKEN}
       - GITEA_RUNNER_NAME=homelab-runner
       - GITEA_RUNNER_LABELS=ubuntu-latest:docker://catthehacker/ubuntu:act-latest
-      - GITEA_RUNNER_CONTAINER_NETWORK=ci
+      - CONFIG_FILE=/config.yaml
     volumes:
       - ${DOCKER_SOCK:-/run/user/1000/docker.sock}:/var/run/docker.sock
       - act_runner_data:/data
+      - ./act-runner/config.yaml:/config.yaml:ro
     depends_on:
       - gitea
     restart: unless-stopped