Fix: Use docker-build label for build job (Docker required)

The build job needs Docker installed, but ubuntu-latest (node:16-bullseye) doesn't have Docker.
Changed build job to use docker-build label with docker:latest image.

NOTE: Runner .env must be updated manually with:
docker-build:docker://docker:latest

Then runner must be re-registered to pick up the new label.

.gitea/workflows/production-deploy.yml

@@ -97,7 +97,7 @@ jobs:
     needs: test
     # Note: if condition might not work correctly in Gitea - always() might need different syntax
     # if: always() && (needs.test.result == 'success' || needs.test.result == 'skipped')
-    runs-on: ubuntu-latest
+    runs-on: docker-build  # Uses docker:dind image with Docker pre-installed
     outputs:
       image_tag: ${{ steps.meta.outputs.tag }}
       commit_sha: ${{ steps.meta.outputs.commit_sha }}