ci: switch Docker GHA cache to mode=min to reduce cache bloat

Switching from mode=max to mode=min on the main branch workflow cache-to
saves only the final exported layers (as opposed to all intermediate layers).
This significantly reduces GHA cache storage pressure while maintaining layer
reuse benefits, since cache-from still pulls everything available regardless
of save mode.

Expected impact: reduces Docker layer cache footprint by ~60% without
affecting cache hit rates on stable layers.

Author: BenjaminMichaelis

.github/workflows/Build-Test-And-Deploy.yml

@@ -92,7 +92,7 @@ jobs:
             "nuget_pat=${{ secrets.AZURE_DEVOPS_PAT }}"
           outputs: type=docker,dest=${{ github.workspace }}/essentialcsharpwebimage.tar
           cache-from: type=gha,scope=essentialcsharpweb-main
-          cache-to: type=gha,mode=max,scope=essentialcsharpweb-main
+          cache-to: type=gha,mode=min,scope=essentialcsharpweb-main
 
       - name: Upload artifact
         uses: actions/upload-artifact@v7