Auto-detect DIND daemon hostname/IP

- Test multiple possible DIND hostnames/IPs
- Try docker-runner.docker.internal, host.docker.internal, 172.17.0.1
- Automatically set DOCKER_HOST when connection succeeds
- Verify with docker version before proceeding

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

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

.forgejo/workflows/docker-build.yml

@@ -10,10 +10,29 @@ jobs:
     runs-on: ubuntu-latest
     container:
       image: docker:latest
-      env:
-        DOCKER_HOST: tcp://docker-runner:2375
 
     steps:
+      - name: Find DIND daemon
+        run: |
+          echo "=== Checking /etc/hosts ==="
+          cat /etc/hosts
+
+          echo ""
+          echo "=== Testing DIND connection options ==="
+
+          # Try different hostnames/IPs
+          for host in docker-runner.docker.internal host.docker.internal 172.17.0.1 gateway.docker.internal; do
+            echo "Testing: $host"
+            if timeout 2 sh -c "cat < /dev/null > /dev/tcp/$host/2375" 2>/dev/null; then
+              echo "✅ SUCCESS: Can reach DIND at $host:2375"
+              echo "DOCKER_HOST=tcp://$host:2375" >> $GITHUB_ENV
+              export DOCKER_HOST=tcp://$host:2375
+              docker version && break
+            else
+              echo "❌ FAILED: Cannot reach $host:2375"
+            fi
+          done
+
       - name: Checkout repository
         run: |
           apk add --no-cache git