chore: update GitHub Actions versions in CI workflow

- checkout@v4 -> v6
- setup-dotnet@v4 -> v5

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: HavenDV

.github/workflows/dotnet.yml

@@ -50,10 +50,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Setup .NET
-        uses: actions/setup-dotnet@v4
+        uses: actions/setup-dotnet@v5
 
       - name: Install AutoSDK CLI
         run: dotnet tool install --global autosdk.cli --prerelease