Update Docker build workflow to trigger only on version tags

- Modify the workflow to prevent builds on branch pushes (dev/main).
- Ensure builds are triggered exclusively when a version tag (v*) is set, aligning with release merges.
- Adjust image tagging logic to enable 'latest' tag only for tagged releases.

.gitea/workflows/docker-build.yml

@@ -1,9 +1,10 @@
 name: Docker Image bauen & veröffentlichen
 
 on:
+  # Kein Build auf Branch-Pushes (dev/main).
+  # Build nur, wenn ein Versions-Tag (v*) gesetzt wird
+  # -> also beim Release-Merge dev -> main inkl. Tag.
   push:
-    branches:
-      - main
     tags:
       - "v*"
   workflow_dispatch:
@@ -40,12 +41,11 @@ jobs:
         with:
           images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
           tags: |
-            type=ref,event=branch
-            type=ref,event=tag
             type=semver,pattern={{version}}
             type=semver,pattern={{major}}.{{minor}}
+            type=semver,pattern={{major}}
             type=sha,format=short
-            type=raw,value=latest,enable={{is_default_branch}}
+            type=raw,value=latest,enable=${{ startsWith(github.ref, 'refs/tags/') }}
 
       - name: Image bauen & pushen
         uses: docker/build-push-action@v6