update workflow

.gitea/workflows/nightly-build.yml

@@ -1,14 +1,14 @@
 name: Nightly Docker Build
 
 on:
-  push:
   schedule:
     - cron: '0 0 * * *'  # Midnight
   workflow_dispatch:     # Allow manual runs
 
 jobs:
   build-and-push:
-    runs-on: alpine:latest
+    container:
+      image: alpine:latest
     steps:
       - name: Install dependencies
         run: apk add docker nodejs