Refactor artifact paths to use github.workspace

Updated the workflow to use github.workspace for artifact paths.

Author: roman-dotsenko

.github/workflows/api_job-helper-app.yml

@@ -28,14 +28,14 @@ jobs:
         working-directory: ./backend
 
       - name: dotnet publish
-        run: dotnet publish -c Release -o "${{env.DOTNET_ROOT}}/myapp"
+        run: dotnet publish -c Release -o ${{github.workspace}}/myapp
         working-directory: ./backend
 
       - name: Upload artifact for deployment job
         uses: actions/upload-artifact@v4
         with:
           name: .net-app
-          path: ${{env.DOTNET_ROOT}}/myapp
+          path: ${{github.workspace}}/myapp
 
   deploy:
     runs-on: windows-latest