fix: hardcode NuGet username

NuGet username is not sensitive, hardcode it directly instead of
requiring a repository secret.

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

Author: JusterZhu

.github/workflows/publish-nuget.yml

@@ -88,7 +88,7 @@ jobs:
         id: nuget-login
         uses: NuGet/login@v1
         with:
-          user: ${{ secrets.NUGET_USER }}
+          user: juster.chu
 
       - name: Push NuGet package to NuGet.org
         if: ${{ inputs.push-to-nuget == true }}