Use docker:latest container with DOCKER_HOST for DIND

- Run workflow in docker:latest container (has docker CLI)
- Set DOCKER_HOST to connect to DIND daemon
- Install git in Alpine container
- Enables Docker commands in job container

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

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

.forgejo/workflows/docker-build.yml

@@ -8,10 +8,15 @@ on:
 jobs:
   build-and-push:
     runs-on: ubuntu-latest
+    container:
+      image: docker:latest
+      env:
+        DOCKER_HOST: tcp://docker-runner:2375
 
     steps:
       - name: Checkout repository
         run: |
+          apk add --no-cache git
           git clone ${{ github.server_url }}/${{ github.repository }} .
           git checkout ${{ github.sha }}
           ls -la