Add docker-build.yml: build + push :latest to registry.alwisp.com on the host runner

.gitea/workflows/docker-build.yml

@@ -0,0 +1,28 @@
+name: Build and Push Docker Image
+
+on:
+  push:
+    branches: [main]
+  workflow_dispatch:
+
+jobs:
+  build:
+    # Runs on the forgerunner host: bundled Docker CLI + mounted /var/run/docker.sock.
+    runs-on: host
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Log in to Gitea Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: registry.alwisp.com
+          username: ${{ secrets.REGISTRY_USER }}
+          password: ${{ secrets.REGISTRY_TOKEN }}
+
+      - name: Build and Push
+        run: |
+          # gitea.repository is already "owner/repo" (e.g. jason/breedr).
+          IMAGE="registry.alwisp.com/${{ gitea.repository }}"
+          docker build -t "${IMAGE}:latest" .
+          docker push "${IMAGE}:latest"