Update docker-build.yml workflow

.gitea/workflows/docker-build.yml

@@ -2,7 +2,7 @@ name: Build and Push Docker Image
 
 on:
   push:
-    branches: [main]
+    branches: [master]
   workflow_dispatch:
 
 jobs:
@@ -26,3 +26,10 @@ jobs:
           IMAGE="registry.alwisp.com/${{ gitea.repository }}"
           docker build -t "${IMAGE}:latest" .
           docker push "${IMAGE}:latest"
+
+      # Dangling-only prune: removes untagged leftovers from previous builds.
+      # Never removes the tagged :latest (kept for the Unraid deployment) or
+      # any image referenced by a container.
+      - name: Prune dangling images on host
+        if: always()
+        run: docker image prune -f 2>/dev/null || true