try

.gitea/workflows/build-an-push.yaml

@@ -4,12 +4,14 @@ on:
   push:
     branches:
       - master
+      
 jobs:
    build:
      runs-on: cth-ubuntu-latest
      steps:
        - name: checkout
          uses: actions/checkout@v4
+         
        - name: setup buildx
          uses: docker/setup-buildx-action@v3
          with:
@@ -17,6 +19,7 @@ jobs:
               [registry."192.168.0.151:32000"]
               http = true
               insecure = true
+              
       - name: Build and push Docker image
         uses: docker/build-push-action@v5
         with: