Use runner's DOCKER_HOST with default ubuntu container

- Remove custom docker:latest container
- Use default ubuntu-latest (should inherit runner's DOCKER_HOST)
- Install docker.io client in job
- Check DOCKER_HOST environment variable
- Should use runner's tcp://docker-runner:2375 config

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

.forgejo/workflows/docker-build.yml

@@ -8,38 +8,23 @@ on:
 jobs:
   build-and-push:
     runs-on: ubuntu-latest
-    container:
-      image: docker:latest
 
     steps:
-      - name: Debug network configuration
+      - name: Set up Docker (use runner's DOCKER_HOST)
         run: |
-          echo "=== Network interfaces and routes ==="
-          ip route show 2>/dev/null || route -n
+          # The runner should have DOCKER_HOST set
+          echo "DOCKER_HOST from runner: ${DOCKER_HOST:-not set}"
 
-          echo ""
-          echo "=== Testing gateway IP directly ==="
-          GATEWAY_IP=$(ip route show | grep default | awk '{print $3}')
-          echo "Gateway IP: $GATEWAY_IP"
-
-          if timeout 2 sh -c "cat < /dev/null > /dev/tcp/$GATEWAY_IP/2375" 2>/dev/null; then
-            echo "✅ Can reach DIND at $GATEWAY_IP:2375"
-            echo "DOCKER_HOST=tcp://$GATEWAY_IP:2375" >> $GITHUB_ENV
-            export DOCKER_HOST=tcp://$GATEWAY_IP:2375
-          else
-            echo "❌ Cannot reach gateway at $GATEWAY_IP:2375"
-            echo "The DIND container might not be accessible from job containers"
-            echo "You may need to configure the runner to use --network=host or expose DIND port on host"
-            exit 1
+          # Install docker client if not present
+          if ! command -v docker &> /dev/null; then
+            echo "Installing docker client..."
+            apt-get update -qq && apt-get install -y -qq docker.io
           fi
 
-      - name: Verify Docker connection
-        run: |
           docker version
 
       - name: Checkout repository
         run: |
-          apk add --no-cache git
           git clone ${{ github.server_url }}/${{ github.repository }} .
           git checkout ${{ github.sha }}
           ls -la