Align setup-node to v6 to match other workflows

Agent-Logs-Url: https://github.com/IntelliTect/EssentialCSharp.Web/sessions/2700a888-9644-4b61-91b0-5a23e223672e

Co-authored-by: BenjaminMichaelis <22186029+BenjaminMichaelis@users.noreply.github.com>

Author: Copilot

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

@@ -12,7 +12,7 @@ jobs:
       - uses: actions/checkout@v6
 
       - name: Set up Node.js
-        uses: actions/setup-node@v4
+        uses: actions/setup-node@v6
         with:
           node-version: '26'
           cache: npm