ci: switch upload to registry to not use separate login

flake.nix

@@ -24,18 +24,22 @@
           # 2. Authenticate if CI environment variables are present
           if [ -n "''${REGISTRY_USERNAME:-}" ] && [ -n "''${REGISTRY_PASSWORD:-}" ]; then
             echo "CI Environment detected: Logging in to registry."
-            ${pkgs.skopeo}/bin/skopeo login gitlab.julian-mutter.de \
-              --username "''${REGISTRY_USERNAME}" \
-              --password "''${REGISTRY_PASSWORD}"
+
+            # 3. Upload to container registry
+            ${pkgs.skopeo}/bin/skopeo copy \
+                --dest-creds "''${REGISTRY_USERNAME}:''${REGISTRY_PASSWORD}" \
+                --insecure-policy \
+                docker-archive:result \
+                docker://gitlab.julian-mutter.de/julian/sheetless-server:latest
           else
             echo "Local Environment detected: Skipping login, relying on existing auth."
-          fi
 
-          # 3. Upload to container registry
-          ${pkgs.skopeo}/bin/skopeo copy \
-              --insecure-policy \
-              docker-archive:result \
-              docker://gitlab.julian-mutter.de/julian/sheetless-server:latest
+            # 3. Upload to container registry
+            ${pkgs.skopeo}/bin/skopeo copy \
+                --insecure-policy \
+                docker-archive:result \
+                docker://gitlab.julian-mutter.de/julian/sheetless-server:latest
+          fi
         '';
       in {
         devShells.default = pkgs.mkShell {