feat: Skip Docker build if image already exists for commit

- Add check step to verify if image for commit SHA already exists
- Skip build step if image exists (saves 5+ minutes per deployment)
- Use git-{SHORT_SHA} tag to identify images by commit
- Only rebuild when code actually changed
- Improve build cache utilization

.gitea/workflows/production-deploy.yml

@@ -100,8 +100,9 @@ jobs:
     # if: always() && (needs.test.result == 'success' || needs.test.result == 'skipped')
     runs-on: docker-build  # Uses docker:dind image with Docker pre-installed
     outputs:
-      image_tag: ${{ steps.meta.outputs.tag }}
+      image_tag: ${{ steps.image_info.outputs.IMAGE_TAG || steps.build_image.outputs.IMAGE_TAG || 'git-' + github.sha }}
       commit_sha: ${{ steps.meta.outputs.commit_sha }}
+      image_built: ${{ steps.check_image.outputs.SKIP_BUILD != 'true' }}
     steps:
       - name: Install git and setup environment
         shell: sh
@@ -521,6 +522,7 @@ jobs:
           TAG="${SHORT_SHA}-$(date +%s)"
           
           # Build with cache - verwende REGISTRY_TO_USE Variable
+          echo "🏗️  Starte Docker Build für Commit ${SHORT_SHA}..."
           docker buildx build \
             --platform linux/amd64 \
             --file ./Dockerfile.production \
@@ -528,6 +530,7 @@ jobs:
             --tag "${REGISTRY_TO_USE}/${IMAGE_NAME}:${TAG}" \
             --tag "${REGISTRY_TO_USE}/${IMAGE_NAME}:git-${SHORT_SHA}" \
             --cache-from type=registry,ref="${REGISTRY_TO_USE}/${IMAGE_NAME}:buildcache" \
+            --cache-from type=registry,ref="${REGISTRY_TO_USE}/${IMAGE_NAME}:latest" \
             --cache-to type=registry,ref="${REGISTRY_TO_USE}/${IMAGE_NAME}:buildcache",mode=max \
             --build-arg BUILD_DATE=$(date -u +'%Y-%m-%dT%H:%M:%SZ') \
             --build-arg GIT_COMMIT=${COMMIT_SHA} \
@@ -535,10 +538,51 @@ jobs:
             --push \
             .
           
+          echo "✅ Image erfolgreich gebaut und gepusht!"
+          
+      - name: Use existing image (skip build)
+        if: steps.check_image.outputs.SKIP_BUILD == 'true'
+        shell: bash
+        run: |
+          echo "✅ Verwende vorhandenes Image: ${{ steps.check_image.outputs.EXISTING_IMAGE }}"
+          echo "📝 Commit: ${{ github.sha }}"
+          echo "🏷️  Image-Tag: ${{ steps.check_image.outputs.IMAGE_TAG }}"
+          echo ""
+          echo "⏭️  Build-Schritt wurde übersprungen, da Image bereits in Registry existiert."
+          echo "💡 Dies spart Zeit und Ressourcen - das Image wird direkt für Deployment verwendet."
+
+      - name: Set image tag for deployment
+        id: image_info
+        shell: bash
+        run: |
+          COMMIT_SHA="${{ github.sha }}"
+          if [ -z "$COMMIT_SHA" ]; then
+            COMMIT_SHA=$(cd /workspace/repo && git rev-parse HEAD)
+          fi
+          SHORT_SHA=$(echo "$COMMIT_SHA" | cut -c1-7)
+          
+          # Verwende vorhandenes Image oder neu gebautes
+          if [ "${{ steps.check_image.outputs.SKIP_BUILD }}" = "true" ]; then
+            IMAGE_TAG="git-${SHORT_SHA}"
+            echo "IMAGE_TAG=$IMAGE_TAG" >> $GITHUB_OUTPUT
+            echo "IMAGE_EXISTS=true" >> $GITHUB_OUTPUT
+          else
+            # Tag aus neuem Build
+            IMAGE_TAG="${SHORT_SHA}-$(date +%s)"
+            echo "IMAGE_TAG=$IMAGE_TAG" >> $GITHUB_OUTPUT
+            echo "IMAGE_EXISTS=false" >> $GITHUB_OUTPUT
+          fi
+          
+          echo "📦 Verwendetes Image-Tag: $IMAGE_TAG"
+
       - name: Image scan for vulnerabilities
         shell: bash
         run: |
-          echo "✅ Image built successfully: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ steps.meta.outputs.tag }}"
+          if [ "${{ steps.check_image.outputs.SKIP_BUILD }}" = "true" ]; then
+            echo "⏭️  Vulnerability scan übersprungen (verwendet vorhandenes Image)"
+          else
+            echo "✅ Image built successfully: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ steps.image_info.outputs.IMAGE_TAG }}"
+          fi
 
   # Job 3: Deploy to Production
   deploy: