feat: Enhance Windows Avalonia build workflow with NuGet source validation and configuration

.forgejo/workflows/build-windows-avalonia.yml

@@ -14,10 +14,15 @@ env:
   PROJECT_PATH: imagecatalog/ImageCatalog 2.csproj
   PUBLISH_DIR: artifacts/publish/win-x64
   ARTIFACT_NAME: imagecatalog-windows-avalonia
+  NUGET_SOURCE_NAME: Nuget-GitLab-AIFotoONLUS
+  NUGET_SOURCE_URL: https://gitlab.com/api/v4/projects/79509532/packages/nuget/index.json
 
 jobs:
   build:
     runs-on: docker
+    env:
+      NUGET_USERNAME: ${{ secrets.NUGET_USERNAME }}
+      NUGET_PASSWORD: ${{ secrets.NUGET_PASSWORD }}
 
     steps:
       - name: Checkout
@@ -28,8 +33,35 @@ jobs:
         with:
           dotnet-version: ${{ env.DOTNET_VERSION }}
 
+      - name: Validate NuGet secrets
+        run: |
+          set -eu
+          if [ -z "${NUGET_USERNAME}" ]; then
+            echo "secrets.NUGET_USERNAME is required"
+            exit 1
+          fi
+          if [ -z "${NUGET_PASSWORD}" ]; then
+            echo "secrets.NUGET_PASSWORD is required"
+            exit 1
+          fi
+
+      - name: Configure private NuGet source
+        run: |
+          set -eu
+          temp_config="${RUNNER_TEMP}/nuget.config"
+          cp NuGet.Config "${temp_config}"
+
+          dotnet nuget update source "${{ env.NUGET_SOURCE_NAME }}" \
+            --source "${{ env.NUGET_SOURCE_URL }}" \
+            --username "${NUGET_USERNAME}" \
+            --password "${NUGET_PASSWORD}" \
+            --store-password-in-clear-text \
+            --configfile "${temp_config}"
+
+          echo "NUGET_CONFIG_PATH=${temp_config}" >> "${GITHUB_ENV}"
+
       - name: Restore
-        run: dotnet restore "${{ env.PROJECT_PATH }}" -r win-x64
+        run: dotnet restore "${{ env.PROJECT_PATH }}" -r win-x64 --configfile "${NUGET_CONFIG_PATH}"
 
       - name: Publish Windows Avalonia build
         run: |
@@ -38,6 +70,7 @@ jobs:
             -c Release \
             -r win-x64 \
             --self-contained true \
+            --no-restore \
             -p:AvaloniaWindowsCrossPublish=true \
             -p:PublishSingleFile=true \
             -p:PublishTrimmed=false \