Fix Docker build: lowercase image name + Feature Requests ergaenzt

- Fix: GHCR image name muss lowercase sein (Kroonk -> kroonk)
- Feature Request: Admin One-Click Update Button hinzugefuegt

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.github/workflows/docker-build.yml

@@ -6,7 +6,6 @@ on:
 
 env:
   REGISTRY: ghcr.io
-  IMAGE_NAME: ${{ github.repository }}
 
 jobs:
   build-and-push:
@@ -26,6 +25,9 @@ jobs:
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
 
+      - name: Lowercase image name
+        run: echo "IMAGE_NAME=$(echo '${{ github.repository }}' | tr '[:upper:]' '[:lower:]')" >> $GITHUB_ENV
+
       - name: Build and push Docker image
         uses: docker/build-push-action@v5
         with: